HOSA State Review

Forensic Careers

• Forensic Psychologist - Psychologist who applies psychology to law/legal proceedings

• Crime Scene Investigator - An expert trained in the use of forensics techniques, such as gathering DNA evidence, collecting fingerprints, photographing the scene, sketching, interviewing witnesses

• Forensic Photographer - The professional that uses a camera to document the crime scene and the evidence found at the crime scene

• Trace Evidence Examiner - Forensic scientist who performs analyses on trace evidence that may occur as a result of physical contact between a suspect and victim during a violent crime

• Latent Fingerprint Examiner - Handles identification processes, including taking photos of fingerprints, utilizing different methods of latent fingerprint identification in the crime scene and identifying the fingerprints by running them against the FBI’s automated fingerprint identification system

• Forensic Serologist - Examines blood and body fluids for clues about the person they came from

• Forensic Toxicologist - Performs tests on bodily fluids, tissues, organs to determine/identify presence of drugs, poison, other chemicals

• Forensic Documents Examiner - Examines paper evidence to determine the source

• Firearm Examiner/Forensic Ballistics Examiner - Examines firearms, discharged ammunition; Conducts distance determination, tool mark examination

• Forensic Entomologist - One who studies bugs; Can determine approximate postmortem interval based on type/stage of insect larvae present

• Digital Forensics Experts/Forensic Computer Investigators - Reconstruct/analyze digital information to aid in investigations, solve computer-related crimes; Look into incidence of hacking, trace sources of computer attacks, recover lost/stolen data

• Forensic Engineer - Deals with investigation of materials, products, structures, components that fail/do not operate right, causing personal injury/damage to property

• Forensic Odontologist - Studies dental profiles, such as those involved with bite mark evidence

• Forensic Pathologist/Medical Examiner - Medical doctor who performs the autopsy on a victim to determine cause of death, manner of death, approximate time of death

• Bloodstain Pattern Analyst - Study blood at crime scenes

• Forensic DNA Analyst - Observes DNA samples found at the scene of a crime, compare it to potential suspects in order to accurately identify an entity; Can work in crime labs or private labs

• Polygraph Examiner - Detects the truth of statements through the use of instrumentation

• Forensic Accountant - Analyzes financial evidence, testifies as an expert witness in cases of white-collar crime (ex. money laundering)

• Forensic Anthropologist - Studies bones; Can help determine age, sex, race, approximate height; Can reconstruct an accurate face from a skull

• Forensic Chemist - Applies principles/techniques of chemistry to evidence like paint, fibers, gunshot residue

• Forensic Artist - Responsible for facial reconstruction/sketching of a crime scene

• Forensic Arson Investigator - Surveys scene of a fire to determine if the fire was accidental or intentional

• Accident Reconstructionist - Has knowledge of both crime scene investigation and math that helps explain circumstances surrounding an accident

Crime-Scene Investigation and Evidence Collection

• Trace Evidence - Transferred materials that occur as a result of physical contact

  • Ex. Pet hair on clothes/rugs

  • Hair on brushes

  • Fingerprints on a glass

  • Soil tracked into homes/buildings

  • Blood on a shirt

• Locard’s Principle of Exchange - When a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur

  • Also states that the intensity, duration, and nature of the entities in contact determine the extent of the transfer

Types of Evidence

• Direct Evidence - Firsthand observations

  • Ex. Eyewitness accounts

  • Police dashboard video cameras

  • Confessions

• Circumstantial Evidence - Indirect evidence that can be used to imply a fact but does not prove it

  • May provide a link between a crime scene and a suspect

  • Ex. Suspect’s gun at the site of a shooting

  • Can be physical or biological in nature

  • Ex. Fingerprints, footprints, weapons, bullets, shell casings

  • Tissue, bodily fluids, hair, plants, natural fibers

• Trace evidence is a type of circumstantial evidence

• Class Evidence - Narrows an identity to a group of persons/things

  • Ex. Blood type

• Individual Evidence - Narrows an identity to a single person/thing

  • Ex. DNA, fingerprints

The Seven S’s of Crime Scene Investigation

• Securing the Scene - Responsibility of the first-responders

  • First priority: Safety of everyone in the area

  • Second priority: Preservation of evidence

  • Officer collects pertinent information, requests additional requirements for investigation, may ask teams of experts to be sent to scene

• Separating the Witnesses - Witnesses cannot talk to each other

  • Witnesses’ accounts of the event will be compared to recreate scene

  • Witnesses are separated so they do not work together to create a story (collusion)

• Scanning the Scene - Scene needs to be scanned to determine where photos should be taken

  • Primary Crime Scene - Location of the crime

  • Secondary Crime Scene -If movement to a new location occurs, that new location is considered a secondary crime scene

• Seeing the Scene - Photos of overall and close-up scene with and without a measuring ruler should be taken

  • Triangulation - Mathematical method of calculating the location of an object from the locations of other objects

• Sketching the Scene - Crime-scene investigator makes a sketch of the crime scene, noting the position of evidence/remains

  • All objects should be measured from two immovable objects

• Searching the Evidence - Search pattern is applied to search for evidence

  • Patterns include: grid, linear, quadrant/zone, spiral

• Securing and Collecting Evidence - All evidence needs to be properly packaged, sealed, labeled, following specific procedures to prevent contamination

  • Moist biological evidence is stored in breathable containers so the evidence can dry out, reducing the chance of mold contamination

  • Then stored in a paper bindle, which is placed in a plastic/paper container that is sealed with tape

  • Signature of the collector must be written across the tape

  • Evidence log and chain of custody document must be attached to the evidence container

- Crime scene investigation can help with linking people, scenes, objects, investigative leads, information of the concrete evidence of a crime (ex. corpse), information on the criminal’s MO, proving/disproving witness statements, identification of suspects, identification of unknown substances, crime reconstruction

Defining the Crime Scene

• Primary Crime Scene - The site of the original/first criminal activity

• Secondary Crime Scene - Any subsequent crime scenes/scenes immediately associated with the crime

• Macroscopic Crime Scene - The general scene of the crime

• Microscopic Crime Scene - The specific pieces of evidence, trace evidence

General Crime Scene Procedures

• Four components of crime scene management: information management, manpower management, technology management, logistics management

• Types of crime scene investigation models:

• Traditional - Uses patrol officers/detectives, useful if resources/demand are low, minimal experience, time conflicts with other duties

• Crime Scene Technicians - Specially trained, full-time civilian personnel, continuity, specialized, minimal investigative experience, lack of global view of investigation

• Major Crime Squad - Full-time, sworn officers, primary assignment, increased experience, depletion of investigative resources

• Lab Crime Scene Scientist - Laboratory scientists, advanced technical knowledge, and skills, no investigative experience, depletion of lab resources

• Collaborative Team - Police officers, technicians, lab personnel, medical examiners, prosecuting authorities, advanced scientific, technical, investigative resources, extensive resources, comprehensive procedures

• First-responders are the first to arrive - do general tasks like securing/assisting victim, detaining/separating witnesses, etc.

• After first-responders, when crime scene investigator arrives, they do a walk-through, the preliminary scene survey, normally collect digital images

Crime Scene Documentation and Forensic Photography

• Four major tasks of documentation: note taking, videography, photography, sketching

• Digital imaging is easy and more convenient than the old-fashioned, outdated film photography

  • Logs/records of any edits to forensic digital images are automatically kept to prevent tampering/make it easier to identify

  • Digital imaging used to provide a true and accurate pictorial record of the crime scene/physical evidence present

  • Used to record initial condition of the scene

  • Every photo taken at the crime scene must be recorded in a photo log including the time taken, camera setting used, indication of distance to subject, type of photograph taken, brief description of the image

• Imaging/mapping technology can be used to create a crime scene map that can sometimes be rendered in 3D

• Forensic notes are taken as activities are done so one doesn’t forget anything by the time they write it down

  • When taking notes, consider who, what, when, where, why, notification information, arrival information, scene description, victim description (don’t move the victim until medical examiner has approved it), crime scene team

• Videography of the scene is very useful for understanding the full crime-scene

  • Videos should not include other personnel on site, equipment, audio narration/explanation of any kind, etc.

  • Video should begin with a placard indicating case number, videographer, date, time, location

  • Camera should move in smooth movements, with tripod/monopod if possible, additional lighting if needed

  • View four compass points from victim’s perspective

  • Original videos are evidence that is admissible in court, should not be edited/tampered with, make copies if needed

• Sketching the crime scene requires accurate measurements, provides a cohesive view of the whole scene with measurements attached

  • Multiple types of perspectives, most common are overhead/birds-eye, elevation/side-view

  • Combination perspective/cross-projection sketch integrates overhead with elevation

  • Three main methods of measurements: triangulation (points X and Y are fixed, evidence A and B is measured from points X and Y), baseline/fixed line (points X and Y are fixed, evidence A and B are measured along the line between X-Y and at right angles to X and Y), polar coordinates (object A is a distance from wall X and is 30 degrees southwest. A transit/compass is used to measure the angles)

    • All involve taking measurements with reference to two fixed points

  • All crime scene sketches require their own documentation

• After documentation, the scene should be searched

  • Most common search methods include grid, line, link, zone, wheel/ray, spiral

Collection and Preservation of Physical Evidence

• Evidence should be collected after documentation/searching

• Most evidence will be packaged in a primary container that is then put into a secondary container

• Druggist’s folds/large pieces of paper can be used as primary containers

• These folds are then put into secondary containers such as envelopes, canisters, paper bags, etc.

• Outer container should be marked with information about the item, identification of collector, date/time where item was collected, location where item was found

• Sealing/evidence tape should completely cover the opening of the secondary container, marked with initials of collector

• Liquid/volatile items should be placed in airtight, unbreakable containers

• Wet, moist, living biological evidence can be temporarily packed in airtight containers

  • Should be allowed to air-dry in controlled environment, repackaged with original container in new permeable containers to allow for a drying air flow

• Each piece of evidence should be packaged separately to prevent cross contamination

Crime Scene Reconstruction

• Crime Scene Reconstruction - Process of determining/eliminating the events that could have occurred at the crime scene by analysis of the crime scene appearance, location, position of evidence, etc.

• Depends on:

  • Data Collection - Collection and analyzation of evidence, witness statements, etc.

  • Conjecture - Possible explanation for what could have happened based on the evidence currently available

  • Hypothesis Formulation - Additional accumulation of data can lead to the formation of a formal hypothesis

  • Testing - Additional testing must be conducted to approve/disprove overall interpretation/specific aspects of the hypothesis; hypothesis is then refined

  • Theory Formulation - Additional information may be received and may need to be incorporated into the hypothesis; When hypothesis has been thoroughly tested and verified, the reconstruction theory can be formulated

Bloodstain Patterns

History of Bloodstain Pattern Analysis

• Dr. Victor Balthazard - Original research/experimentation with bloodstain analysis

• Use of bloodstain pattern analysis became a recognized forensic discipline in 1955, when Dr. Paul Kirk at UCBerekely submitted an affidavit with his bloodstain analysis findings in the case of State of Ohio v. Samuel Sheppard

• Scientific Working Group on Bloodstain Pattern Analysis (SWGSTAIN) was formed to further develop and standardize bloodstain pattern analysis

Properties of Human Blood

• Plasma - Liquid part of blood that contains red blood cells (RBCs), white blood cells (WBCs), platelets

• Serum - The liquid part of the blood that doesn’t clot

• Nuclei of WBCs are the source of DNA in the blood

• Cellular components are around 45% of the total blood volume in most people (around 4.5-6 liters)

• Exsanguination - Bleeding to death

• Surface tension of blood is slightly less than that of water

• Blood falls in a spheroid shape, not a teardrop shape

• The volume of a blood drop depends on the surface from which it is falling (ex. a drop of blood falling off a human finger will be bigger than one from a needle and smaller from one off a baseball bat)

• The typical volume of a blood drop is 0.05 mL, with an average diameter of 4.5 mm (while in the air)

  • Can vary

• Blood is almost 6 times as viscous as water

• Viscosity and specific gravity help blood maintain its stability and resist alteration

• Terminal Velocity - The velocity at which the force of air resistance that opposes the drop of blood is equal to the force of the downward gravitational pull

• Practically not possible to establish (confidently) the distance from which a drop of blood has fallen, since the volume of the original drop is not known

Formation of Bloodstains and Bloodstain Patterns

• For there to be spatter, the surface tension of the blood drop has to be broken

• The surface that the drop lands on will cause varying amounts of spatter

• Generally, hard, smooth, nonporous surfaces (like clean glass, smooth tile), will create little to no spatter

• Rough textures (wood, concrete) can create significant amount of spatter because they have protuberances that can break the surface tension of blood in irregular ways

• Narrow end (tail) of an elongated bloodstain points in the direction of travel of the blood (directionality)

• Area of Convergence - General area (in 2D) where the blood originated from

  • Found by drawing straight lines through the long axes of the blood stains, point where they all converge is point of convergence

  • Note that area of convergence in a general area, not a point

• Area of Origin - Location of the blood source in 3D

  • Found by establishing impact angles of representative bloodstains and projecting their trajectories back to a common axis extended up 90 degrees from the 2D area of convergence (along the z-axis)

• Angle of Impact - Angle at which the blood drop hits the surface

  • If angle of impact if 90 degrees, blood stain is generally circular

  • If less than 90, blood stain is generally elliptical

• To calculate angle of impact:

  • Divide width by length to get a ratio less than 1

  • This ratio is the arcsine of the impact angle, impact angle can then be calculated

  • Arcsin(w/l) = angle of impact

• Size, quantity, distribution of blood spatter depends on:

  • Quantity of blood subjected to impact

  • Force of impact

  • Texture of the surface impacted by the blood

• If spatter was created by:

  • Secondary mechanisms, will result in satellite spatter

  • Impact mechanisms, results in gunshot, beating/stabbing, power tools, etc. spatter

  • Projection mechanisms, results in cast-off, arterial, expirated blood

• Forward Spatter - Bloodstain pattern that results from the blood drops traveling the same direction as the impact force; Associated with exit wounds

• Back Spatter - Bloodstain patter from blood that was projected towards the source of the force; Associated with entrance wounds

• Back spatter is normally seen in less quantity than forward spatter

• Rouging Effect - Mist-like dispersion of minute stains, often found in gunshot spatter patterns

• Misting Effect - The mist-like dispersion of blood spatter less than 0.1 mm in diameter

  • Associated with gunshot wounds, not found in beatings, stabbings, etc.

• Satellite Spatter - Spatter produced by blood dripping onto surface or into blood

• Impact spatters associated with gunshot often have a wide size range (less than 0.1 mm to several millimeters or more)

  • Range depends on quantity of blood, caliber of weapon, location/number of shots, impeding factors (hair, clothes, etc.)

• Impact spatter associated with beating/stabbing normally has a size range of 1-3 mm in diameter

  • May change based on force of impact, quantity of available blood, etc.

• There must be exposed blood for impact spatter to be created

• The weapon used, number of blows, etc. affect the resulting pattern

• Drip Patterns - Made when multiple free-falling drops of blood are produced from a stationary source onto a horizontal surface

  • Large, irregular in shape, with small satellite spatters around the periphery of central parent stain on horizontal, nearby vertical surfaces

• Satellite spatters are the result of smaller droplets of blood that have detached from the main blood volume at the moment of impact

  • Circular to oval in shape, diameters ranging from 0.1-2.0 mm

  • Influenced by blood drop volume, freshness of blood, surface texture, distance of vertical target from impact site

  • Vertical height of satellite spatter that was created from a single drop of blood impacting concrete can be as high as 12 inches

• Castoff Pattern - Pattern/blood spatter that results from blood being flung off the weapon being used (in blunt force, stabbing, etc.)

  • Blood droplets fly off the weapon at the angle at which the weapon is being swung

  • Size, distribution, quantity of droplets may vary

  • Often seen in conjunction with impact splatters

  • Cannot be used to determine if person is right-handed or left-handed, is very inaccurate

• Splashed Bloodstain Pattern - Produced when a quantity of blood greater than 1.0 mL is subjected to minor force/allowed to fall freely on a surface

  • Large central areas with peripheral spatters shaped as elongated bloodstains

  • Secondary blood splashing/ricochet may occur as a result of the deflection from one surface to another of large volumes of blood after impact

• Splash patterns can be made by the movement of the victim/assailant when large enough amounts of blood have been spilled

• Projected Bloodstain Pattern - Produced when blood is projected/released as the result of force exceeding that of gravity

  • When enough blood is projected horizontally or downwards at a force greater than that of gravity, the bloodstains have numerous spine-like projections with narrow streaking of the secondary spatters

• Expirated Bloodstain Pattern - When blood is expelled from the nose or mouth to clear the airways

  • Happens due to trauma/injury that results in blood in the mouth, sinuses, airways; blood is expelled in an attempt to clear them

  • Blood may be diluted if mixed with sufficient saliva/nasal secretions before being expelled

  • If blood has been recently expelled, it may contain air bubbles; After the blood has dried and air bubbles have ruptured, they appear as vacuoles

  • Dilution, air bubbles not always present; May indicate expirated blood but cannot be conclusive proof

• Arterial Bloodstain Patterns - Bloodstains that occur from damage to an artery

  • May range from gushing/spurting patterns to small sprays

  • Depends on severity of damage to artery, size/location of artery, whether injury was covered by clothing, location of victim, etc.

  • Should be corroborated with damage to artery found in autopsy

Transfer Bloodstain Patterns - When an object wet with blood comes into contact with another object and leaves an impression

• May give examiner an idea as to what left the impression (hair, knife, etc.)

• Often need to run experiments to find out the if the suspected object actually could leave such an impression

• Can present class/individual evidence if finger, palm, foot, footwear transfers are present

• Partial transfers are often chemically enhanced to resolve additional detail

• Differentiating between transfer and impact spatter on a person’s clothing can tell if they were the perpetrator or just someone who came into contact with the blood (ex. impact spatter normally means they were close to the person when the impact was occurring, transfer may have just been an accident)

• Determining if bloodstain on clothes is spatter or transfer often requires experimentation and microscopic examination

Altered Bloodstains

• The time is takes for blood to dry depends on the amount of blood, surrounding environmental conditions, nature of target surface texture, etc.

• Small spatters can dry in a few minutes, while larger ones can take much longer to dry

• Bloodstains dry from the outside in

• Skeletonized Bloodstain - When the center of a dried bloodstain flakes away, leaving the dried peripheral ring

  • Can also be caused by contact/a wiping motion that leaves the periphery intact; Can be interpreted as movement/activity by the victim/assailant when or after injuries occurred

• Dried bloodstains go through color progression from red to reddish brown to black

  • Estimation of age of bloodstain based on color is difficult because different environmental conditions have different effects on bloodstain color

  • Experimentation is needed to estimate age

• Blood also begins to clot after leaving the body

  • Average clotting time of blood is 3-15 minutes

  • Clots of blood may show drag patterns that indicate additional activity after a significant amount of time has passed

  • Expirated clotted blood may indicate post-injury survival time of the victim

  • As clot progress, it retracts and forces serum away from it

• Moisture (rain, snow, etc.) can also alter/dilute bloodstains

• Diluted bloodstains may be impossible to find without chemical luminol treatment

• Bloodstains covered with soot from a fire may be completely missed

• Heat/fire may cause existing bloodstains to fade, darken, or be completely destroyed

• Void Areas - Absences of bloodstains in otherwise continuous patterns of staining

  • Commonly seen in areas where an object has been removed after spattering of blood

  • Allows analyst to establish sequencing, identify alterations

  • Void areas may be used to establish where the blood-spattering event occurred when there is enough blood

Analysis of Bloodstains on Clothing and Footwear

• Passive Bloodstaining - Transfer, flow patterns, saturation stains, stains resulting from dripping blood

• Active Bloodstaining - Impact spatter, arterial spurts, expirated bloodstains, castoff, etc.

• Bloodstain analysis on clothing often focuses on corroborating/disproving the suspect’s version of how the blood got on their clothes

• Bloodstain analysis on clothes can be difficult, often requires experimentation/testing

Death Investigation

Systems of Death Investigation

• Coroner - Government agent in charge of death investigations; very unstandardized, no specific training required

• Massachusetts was the first to replace the coroner with medical examiners and require that they be licensed (1877)

• Forensic Pathologists - Physicians specializing in pathology and then subspecialize in the borderline area between law and medicine that emphasizes the determination of the cause of death

  • Commonly used in cases of sudden and suspicious deaths

Investigation of Death

• Goal of death investigation - To determine cause, manner, mechanism, (possibly) time of death

• Cause of Death - Disease/injury that initiated lethal chain of events that led to death (the underlying cause)

  • Injury takes precedence over disease in determining cause of death

• Mechanism of Death - Biochemical or physiologic abnormality produced by cause of death that is incompatible with life (ex. limited blood flow to the brain, internal bleeding, etc.)

• Manner of Death - The fashion in which the cause of death came to be

  • Categories: Natural, accidental, homicidal, suicidal, undetermined (NASHU)

  • Natural deaths - Deaths caused solely by disease, without the intervention of trauma

  • Accidental deaths - Deaths from trauma caused by events that no reasonable person would feel had a high probability of causing injury/death

  • Homicidal/Suicidal deaths - Death from trauma caused by events that a reasonable person would think has a high probability of causing injury/death

    • If deceased took the fatal action, death is a suicide

    • If someone other than the deceased took the action, death is a homicide

• Rigor Mortis - A stiffening of the muscles that occurs following death

  • Caused by a chemical reaction that occurs when ATP (commonly used for energy for muscles to contract) is used up and not replenished

    • Normally occurs by 4 hours, but can occur faster if ATP was already depleted by exercise, etc. (called instant rigor mortis)

    • Electric shock can also cause faster rigor mortis

    • Normally disappears by 24-36 hours after death as further decomposition of muscles leads to their inability to remain fixed in rigor

• Livor Mortis - Discoloration of body that occurs of settling of red blood cells after blood stops circulating

  • Occurs within minutes of death when blood cells have increased sedimentation rate due to disease

  • Otherwise, generally seen within an hour or so (on some dark-skinned people, may not be possible to see lividity)

  • May not be able to see lividity if person has died and lost most of their blood volume

  • Lividity becomes fixed (not able to be blanched by finger pressure) after about 12 hours

  • Slowly disappears with decomposition after 36 hours

• Algor Mortis - Cooling of the body after death

  • Generally (for nearly nude body in around 18-20 degree Celsius) -1.4 degrees for first 8 hours

  • Normal body temperature: 37 Celsius/98.6 Fahrenheit

  • Environmental conditions, etc. contribute to cooling

Tools of Death Investigation

• For a death to be worth investigating, must be both sudden and unexpected

• Sudden Death - Death occurring a few hours after symptoms onset

• Unexpected Death - Normally found by examining medical history

  • If death is expected (ex. deceased has history of cardiovascular disease), death is not worth investigating, even if it was sudden

• Medical history also examined to see if cause of death is attributable to delayed effects of injury

• Review of medical history extremely important when people have been treated after injuries

• Reviewing witness statements is important because it provides a record of the deceased’s manner and activities before injury/death

  • Can potentially bias forensic pathologist

  • Generally works best when witness statements are scientifically testable

• Scene examination is very important

  • Forensic pathologist is not always called to scene (too expensive), normally only called to ones that are unique/complicated

  • Photos from crime scene investigators can make up for this, but perspective of forensic pathologist on the scene is unique

Autopsy

• Autopsies in US normally conducted using an inframammary incision - cut beginning at top of each shoulder to midline of upper chest to pubic bone

  • T-shaped

• Examination of brain - incision made behind one ear to behind the other ear, scalp peeled upwards and backwards, sawing the skull in circular/tonsorial cut, removing skull cap

  • Brain can be immediately dissected or placed in formaldehyde to fixate (harden) and prevent further decomposition

• After removal, organs are weighed and dissected to determine disease/injury

• Additional dissections may be done based on situation

  • Posterior neck dissection commonly done in cases of suspected child abuse to look for any damage to muscles, ligaments, etc.

  • If blood clots are found in the lungs, dissection of the legs is generally done because clots often originate in the legs

• During autopsy, syringe and needle is used to remove urine from bladder for testing

  • Blood usually taken from aorta and/or large veins

  • Venous blood considered more reliable than aorta/heart blood for many drugs

  • Blood/urine commonly used to test for drugs of abuse

  • Bile taken from gallbladder

  • Alcohol measured in blood

  • Opiates, diazepines, cocaine measured in urine

• Tissue sections may be taken, coated in paraffin, sliced very thin to be inspected under a light microscope

• Blood/hair may be taken and preserved in an envelope for later DNA testing

• Cut hair contains mtDNA

Investigation of Traumatic Death

• Traumatic deaths may be classified as mechanical, thermal, electrical, or chemical

• Asphyxial Death - Death caused by interference with oxygenation of the brain

  • Can occur from mechanical (strangulation), chemical (cyanide poisoning), and electrical causes (low-voltage electrocution)

• Mechanical Trauma - Includes sharp force and blunt force trauma

  • Blunt Force Trauma - Includes non-firearm and firearm groups

    • Firearm trauma - Can be divided into low velocity and high velocity

• Trauma can be penetrating or non-penetrating

  • Penetrating trauma - Ex. Gunshot, stab wounds

  • Non-penetrating trauma - Ex. Motor vehicle collisions, falls

• Blunt objects produce lacerations and sharp objects produce incised wounds

• Sharp trauma normally causes death by exsanguination (bleeding out), so the heart or a major artery must be damaged to produce death from sharp trauma

• Blunt force trauma causes death most commonly by damaging the brain

• Firearms are the most common suicidal and homicidal wounds seen in the US

• Lethality of a gunshot wound increases with the square of its velocity (from kinetic energy)

• Cutoff between high and low velocity is generally 300 m/s

• Lead Snowstorm - Fragments of lead normally found inside the body from high speed projectiles

• Penetrating Gunshot Wound - Has an entrance and an exit wound, bullet is found

• Perforating Gunshot Wound - Has an entrance and an exit would, but no bullet is found

• Gunshot wounds can help with distance determination - how far away killer was from victim

• Effects of gas (released when bullet is shot) on person is indication of a close or near-contact wound

  • Results in blackening of the skin, variable amounts of laceration (because gas blown into wound tears skin apart), and carboxyhemoglobin (bright red substance formed when carbon monoxide reacts to the hemoglobin and myoglobin in the blood

• Large lacerations are common with gunshot wounds because of the tearing characteristics of the scalp

  • Explosion of the head, evacuation of the brain are common with gunshots that produce large amounts of gas

• As distance from barrel to skin increases, the effect of the gas diminishes

• Unburned powder that penetrates the skin can produce stippling/tattooing around the defect produced by the bullet

  • Referred to as intermediate gunshot wounds, can normally occur when distance between skin and muzzle is between 0.5 cm to 1 m, depending on type of gun

• Distant Gunshot Wounds - Lack smoke and powder effects

  • Only effect of the bullet is visible

  • Range is indeterminate

  • Typical distant wound has a circular skin defect and a rim of abraded (scraped) skin around the edges

  • Estimate of size of bullet is not reliable based on bullet wound alone

    • Elasticity of skin plays a role in size of bullet (younger people have most elastic skin, so their bullet wound will appear smaller), subtle variation in bullet sizes (ex. a 0.2 in difference) also contribute

• Gunshot wounds are typically lacerated

  • Convention is that exit wounds are larger than entrance wounds, but this is not always the case, especially with contact wounds (common in suicides)

• Gunshots wounds with a few side lacerations are normally caused by slow moving projectiles, while wounds with a lot of side lacerations are normally caused by high velocity projectiles

• A shored gunshot wound occurs when the site of the exit is pressed against something else (ex. wall, tight clothing, etc.)

• Rim of abrasion is often wider in shored exit than in entrance wounds

• All entrance wounds are shored by underlying tissue, explaining why a rim of abrasion appears around all entrance wounds

• Rectangular/bullet-shaped exit wounds indicate the bullet was yawing, and that can only happen if the bullet passes through a medium more viscous than air or if it hits something else before hitting the target

• Supported Exit Wounds - Bullets that have passed through a person

• Bullets travel through the body much faster than tissues can tear

• How destructive a bullet is is determined by how much kinetic energy it loses in the body

  • Because of this, some bullets are made to expand in the body so they do not exit, because exiting bullets waste kinetic energy

• The common mechanism of death in cases of blunt force trauma to the head is drowning from aspiration of blood

• Blunt force to the head fractures the bone that forms the roof of the mouth and the nose, and blood spills through the broken bone from veins at the base of the brain that are lacerated as a result of the fractures

  • This blood travels down the throat into the lungs, and the person dies by drowning

• If person is conscious, there will commonly be defense wounds on the little finger side of the forearm from when the person tried to defend themselves during the blunt force trauma

• If person is subdued with physical or chemical means, defense wounds may not be present

  • Alcohol is commonly used as a chemical restraint; Severe intoxication slows reaction time dramatically

• Contusion - An accumulation of blood in the tissues outside the blood vessels, commonly cause by blunt force that breaks small blood vessels

  • Striking pattern may be transferred onto person that has been struck, helping to identify the weapon

• Hematoma - Contusions with more blood

• Alcohol is the most common drug of abuse

• At 0.03% BAC (blood alcohol concentration), a slight increase in reaction time is noted, probably due to the slowing down of inhibitory neurons

• Above 0.03%, reaction time slows, brain function slows

• At around 0.25%, a person who has not been exposed previously to alcohol will go into a coma if not stimulated; stimulation will help them regain consciousness

• At around 0.30%, the person will be in a deep coma, cannot be roused, and will generally die of asphyxiation from the slowing down of the central nervous system

• Alcohol overdoses are hard because at around 0.10% the body will start vomiting and alcohol absorption will stop

  • Overdose generally happens when too much is consumed very rapidly, so that it overpowers the vomiting reflex before it can happen

• People who consume alcohol and most other drugs of abuse develop a tolerance, so the numbers above are for those that are not heavy/regular drinkers

• Barbiturates, diazepams, opiates, other depressants all have a similar mechanism of death to alcohol

• Cocaine overdoses are unusual and more uncommon; mechanism of death can be the resulting seizures, high body temperature, and uncontrolled quivering of the heart that occur at large doses

• Carbon monoxide (while not considered a drug of abuse) can also cause death by interfering with oxygenation of the brain

  • Naturally produced in small amounts in our bodies through a process used to make porphyrin, a part of hemoglobin

  • People who commonly smoke tobacco products normally have CO levels above 2% and as high as 10%

  • Levels of CO in people trapped in fires commonly reaches around 90% before person stops breathing and exposes their blood to CO

  • Used to commonly used in suicide; harder to do so now

• Cyanide also interferes with oxygenation of the brain

  • Can also be produced by burning, but its contribution in deaths by fire is less important

  • Has a distinctive smell (like almonds), but cannot be smelled by over 50% of population

  • Can cause intense red color/gastritis in the stomach

• Hypothermia - Death from intense cold

  • Alcohol increases one’s chances of hypothermia because dilated blood vessels result in faster loss of heat

• Hyperthermia - Death from intense heat

  • Common in elderly in the north (in cases where dwelling places aren’t air-conditioned) since ability to maintain homeostasis declines with age

  • Common in infants trapped in cars

• Hypothermia, hyperthermia are difficult to definitely state as cause of death, since there aren’t many symptoms

  • Must rule out all other causes of death and must have a history of being in a location where exposures to such temperatures are possible

• Thermal burns - Localized wounds caused by hyperthermia (can occur when in contact with objects above 65 C/150 F for a few minutes

  • Deaths from thermal burns are normally delayed; mechanism of death is normally multiple organ failure

• People who die at scenes of fire generally die from inhalation of products of combustion (most common is CO)

  • Person’s levels of CO can determine if they died before or after being in fire

    • Levels of 1-2% CO indicate death before fire, since they stopped breathing before they could inhale the CO from the fire

    • Exceptions with gasoline fires

• When exposed to low-voltage alternating currents (AC), the heart will experience ventricular fibrillation, a quivering that leads to non-resuscitability in minutes

• Low voltage normally requires many seconds of exposure to cause electrical burns

• High voltage current sends the heart into tetany, a sustained contraction that is broken when the circuit is broken

• Electrical burns happen in a fraction of a second with high voltage

• The flow of high voltage through tissues causes holes in the membranes of cells (poration), causes loss of limbs

• Asphyxiation can occur by drowning as well

• When drowning:

  • Water that enters the back of the throat is reflexively swallowed, transmitting the negative pressure associated with trying to inhale water to the middle ear via the Eustachian tubes that open during swallowing

  • Swallowed water enters the stomach

  • Further efforts to breathe cause water to enter the upper air passages, triggering coughing and more reflex inhalation

  • As water enters smaller air passages, lining muscles go into spasm in an attempt to protect the alveoli (small air sacs) from anything but air

  • Loss of consciousness generally occurs within 1-2 minutes of this struggle (can be extended is oxygen is obtained)

  • Heart cessation occurs a few minutes later

  • Heart continues to beat, but pressure increases greatly, right side dilates from increased pressure/blood volume from water absorbed from lungs

• To determine death by asphyxiation from drowning, the symptoms will vary, but some include:

  • Negative pressure in ears along with other factors result in hemorrhaging into the mastoid air sinuses

  • Water in sinuses/stomach

  • Diatoms - Single-celled organisms commonly found in fresh and salt water that have silica in their cell walls and can therefore resist acids

  • During late stages of drowning, heart beats water containing diatoms throughout the body

  • Bone marrow sample is examined for diatoms; if present, drowning is generally confirmed

  • Types of diatoms vary with location and time of day, so they can provide information about that

• Manual Strangulation - Compression of neck to constrict the airway

• Doesn’t commonly result in a fractured hyoid bone

  • Only common in elderly women with osteoporosis

• If there is no hemorrhage around fracture in hyoid bone, it occurred after death (possibly during examination during autopsy)

• More common in manual strangulation is the fracture of the cornu of the thyroid cartilage

  • Cornu is in the larynx/voice box and rests against the front of the cervical spine

  • If throat is squeezed to close the air passage, the cornu is pressed backward against the front of the spine

• Common to find hemorrhage in muscles of the neck (collectively called strap muscles) and are bruised

• Ligature Strangulation - Ex. Hanging, garroting

  • Normally only signs are asphyxia and presence of a furrow in the neck

Forensic Anthropology

• Human skeleton has approximately 206 bones (babies have more because not all of their bones have fused together yet)

• Taphonomy - Postmortem changes

• Forensic anthropologists commonly participate in the search for the remains, as it allows them the chance to gain insight into the conditions the body was exposed to postmortem, which may influence their decision

  • Generally identifies if any remains found are human or not and keeps track of which skeletal elements are present

• A grid is generally overlayed onto the search area (can be physical or computerized)

• Bones of several animals can look similar to those of humans, which is why it is very important that forensic anthropologists be able to identify if a bone is human or not

• Forensic anthropologists can also generally identify if remains are of forensic importance or if they are historic/prehistoric graves, although unexpected or unmarked remains would normally be turned over to a medical examiner/coroner first

• Taphonomic Context - The immediate environment and surroundings where the body is found

• The taphonomic conditions of the remains are important in determining time of death, cause of death, etc.

• If the body is still in the early stages of decomposition, soft tissue can be analyzed (may require collaboration with a forensic pathologist)

• Forensic anthropologists may be able to develop a biological profile for the deceased based on their remains (age, gender, sex, etc.)

• Stature is estimated by measuring total body/skeletal length or by extrapolating from long bone lengths

• Unique antemortem characteristics are also used in creating this profile

• Size is used as a common indicator of age in infants and children

  • Diaphyses - Length of long bone shafts

    • Can be used to extrapolate stature

  • In long bones, bony tissue grows from the diaphysis and an epiphysis at either end

    • Grows separately from the diaphysis until human is fully grown, at which point they grow together

  • As ossification centers grow, they gradually replace cartilage

  • The timing of the formation, growth, and fusion of ossification centers is patterned and depends on age, sex, bone element, nutritional/hormonal status, individual variation

  • Females generally develop a bit earlier than males on average

  • Bone development sequences and timing differ slightly from one population to another

  • Age estimates should always be expressed as ranges and should utilize as many indicators as possible for a single set of remains because of the wide variability in factors that determine bone development

  • Patterns of tooth development also differ slightly by sex and population (females develop a bit earlier)

  • In the deciduous dentition, the dental formula for each quadrant is 2.1.2 (2 incisors, 1 canine, 2 molars)

  • In the permanent dentition, the dental formula for each quadrant is 2.1.2.3 (2 incisors, 1 canine, 2 premolars, 2 molars)

  • Agenesis - When the third molars (wisdom teeth) never form/never erupt

  • Individuals of Asian/Native American ancestry commonly have a trait called shoveling, where anterior teeth are slightly thicker (ridges) around the margins of each tooth on the tongue side

    • Not universal in these populations, and can occasionally be found in members of other groups

  • Dental remains are generally more accurate in estimating age in children than bone development for children; however, both must be used in conjunction for the most accurate result

  • Bone density peaks in the 20s and stays high in the 30s, begins to decline in the 40s

    • Declines sharply during menopause in females, levels off after but still declines

    • Males over 40 experience a gradual decline in bone density into old age

  • Bone density depends on factors other than age and hormonal status, like nutrition and weight-bearing exercise

  • Bone density can be observed macroscopically, radiographically, microscopically, or via bone densitometry

  • Macroscopic assessments look at the thinning of the outer bone layer (cortical bone) the trabecular bone (spongy bone), remodeling (changing bone shape) and evidence of fractures

  • Radiographic assessments look at the same thing through X-rays

    • Both are not standardized

  • Bone densitometry measurements are standardized by age, sex, site, population

  • Microscopic measures involve viewing a fixed and decalcified section one of the major long bones and counting bone development structures called osteons that increase with age

  • Osteoporosis - A condition involving low bone density

  • Osteoarthritis - Deterioration in joint integrity connected with use/wear and made worse by inflammation; Related to reduction in bone density after age 40

  • Pubic Symphysis - Area where the left and right pelvis halves join in the front of the body; Consists of two flattened ends connected by cartilage

    • One of the most reliable indicators of age

  • With age, shape of the pubic symphysis changes from billowed to more flattened and rimmed

  • Changes have been divided into age and sex-associated stages

  • There are also standards for the fourth rib nearest the breastbone/sternum and the cranial bones, which suture together with age

  • Sexual Dimorphism - Differences in size and shape between the sexes

  • Determining biological sex from remains can be difficult because of the morphological overlap between the two sexes

    • Morphologies become more different during puberty

  • Skull and pelvis are the most sexually dimorphic skeletal areas, although is it better to examine the entire skeleton for indicators

  • Pelvis allows for childbirth and is critical in posture and standing/walking upright, since it supports the entirety of the upper body

  • Female pelvis has additional breadth and increased diameter of pelvic inlet and outlet to enable childbirth

    • Association female traits include: broad, shallow sciatic notch, U-shaped subpubic angle, well-developed ventral arc

  • Male skull is generally larger with greater muscularity, more robust at areas of muscle attachment (brow ridges, chin), more right-angled at lower jaw, has larger join surfaces where mandible connects to braincase/cranium

  • Postcranial (below the skull) skeleton is generally larger in males

    • Generally have larger weight-bearing joint surfaces, more accentuated areas of muscle attachment, larger diameters of long bones, greater stature

    • Traits vary between populations, are related to nutritional status and behavior

  • Metric Traits - Traits that can be measured

  • Nonmetric Traits - Traits that are described as present or absent

  • One method of forensic ancestry attribution measures the flatness of a face using a specialized instrument called a simometer

  • Western European ancestry is frequently associated with a facial morphology that includes a pinched nasal bridge and a narrow nasal opening, whereas in Asian/Native American populations, the nasal bridge is more apt to be flattened and the nose broader

  • Race cannot be determined from morphological observations

  • To determine stature (which is often done inaccurately), if the body is still essentially complete, the length can be measured; if the body is skeletal and the joints are no longer held together with soft tissue (disarticulated) but some long bones are present, formulas can be used to estimate the stature

  • These formulas use reference populations of known stature (ex. military casualties, modern forensic case databases)

  • Allometry - The presence of patterned and proportional relationships between the sizes of body parts

    • Very important in determining stature from the length of a long bone

    • Note that there is variability in allometry between individuals and between populations

    • Estimates generally require a presumed ancestral population (ex. African-Americans)

    • Osteometry - Specialized measurements of the bones

      • Measurements must be done in specific ways to use the stature formulas so they are taken the same way the data for the reference population was taken

  • Positive Identification (of a person) - Identification beyond a reasonable doubt

    • Generally requires DNA analysis, fingerprints, dental records, X-rays, uniquely identifiable medical apparatus (ex. prosthetics), etc.

  • Facial Approximation - Recreating the soft tissue appearance based on the shape of the bones of the face

  • Skull, cast of skull, digital image of skull can be used as a base, with layers of soft tissue added on with clay or digitally according to the presumed ancestry and the average tissue thickness at multiple points

  • Can also be done by drawing to make a 2-D version

  • Not a means of positive identification

    • Features commonly associated with a specific ancestral population may not have actually been present in the deceased

    • Average tissue thickness will be an underestimate in people with substantial body fat

    • Things like hair length, glasses, facial hair, etc. will have to be guessed at

  • Congenital Anomaly - Birth defect (ex. cleft palate)

    • Might have been noticeable by friends, family, or found in medical record

    • Can be used as source of identification

  • Pathological and other antemortem indicators may or may not have been known by family and friends (ex. visible scars on bone from a surgical procedure, implanted device with a unique identification number, etc.)

  • Evidence falls into three levels of certainty:

    • Possible - Where the biological and medical profile for this set of remains is consistent with the characteristic reported for a given individual

    • Probable - Where it is more probable than not that this individual is so-and-so

      • Often includes circumstantial evidence such as identifiable clothing, presence of a medical condition, identification card

    • Certainty - Beyond a reasonable doubt

      • Includes identification by fingerprint, X-ray, dental match, DNA match, etc.

  • Callus - Bony scar

  • By noting the presence of active/previous bone remodeling (ex. callus at the site of a fracture), anthropologist can assign a traumatic injury to the antemortem period

  • Perimortem trauma must be differentiated from postmortem trauma from flowing water, carnivores, scavengers, etc.

    • Can be done by noting patterns of bone breakage in relation to moisture and fat loss, differential staining on fracture margins, signature modifications of scavengers, plants, geological processes

  • Bone damage with no sigs of healing, which apparently occurred when the bone was still fresh and for which a taphonomic cause can be ruled out, is described as perimortem trauma, meaning it is unclear whether the trauma happened right before or right after death

  • Bone does not exhibit a detectable vital reaction without several days of healing time

  • Blunt force generally leaves impact marks/fractures and can fragment bone

    • Can be delivered by fast or slow impact

    • Speed of impact (fast or slow) can often be determined by plastic deformation (warping of the fragments), which is often more common with slow impact trauma

    • Patterns of trauma can sometimes indicate object shape

  • Gunshot wound is a special type of blunt force trauma

    • Entrance wounds in bones are generally beveled inward and exit wounds are generally beveled outward

    • Due to the slower speed of the radiating fractures compared to the projectile speed, and the fact that fracture lines are halted when encountering other fracture lines, the sequence of gunshots can often be determined

  • Equifinality - When different agents of bone modification produce similar types of damage

Forensic Entomology

• Modern forensic entomology was founded by Jean-Pierre Megnin in France

• Entomologists normally called in when time of death is unknown

Estimating Minimum Elapsed Time Since Death

• The first insects attracted to dead remains are normally the common fly (Diptera in the blow fly family)

• Attracted to carcasses because when first hatched their genetalia are not fully developed, so the carcass serves as a protein meal while it develops

• Dead bodies give off chemical cues immediately after death that humans can’t sense but female blowflies can, indicating that there is a viable source for their offspring

• Blowflies are not active during winter in much of North America (it gets too cold)

• Blowflies are diurnal (active during the day, sleep at night)

• As long as season, temperature, time of day are favorable, blowflies will arrive on a body soon after death (within minutes)

  • If death occurs at night, no blowflies will be present until morning

• Blowflies are attracted to a wound first, since blood is a good protein for their maggots

  • Fun fact: they are so good at finding wounds that they can located a venipuncture (needle mark) when it is no longer visible to the naked eye

• If no wounds are present, maggots will be laid in natural orifices

  • Most contain a mucus lining which is much easier for the maggots to break compared to hard human skin

• Female blowfly leaves after laying eggs

• Blowflies go through three instars/stages of maggots, puparial stage, become adults

  • Very predictable

• Development depends on temperature

  • As temperature increases, insects develop more rapidly, and vice versa (relationship between temperature and development is nearly linear)

  • Also depends on species, nutrition, humidity, etc.

• First Instar - First-stage maggots feed on liquid protein, soon molts into second instar

• Second Instar - Sheds first instar larval cuticle and mouthparts, feeds for some time, moves into third instar

• Third Instar - Sheds cuticle and mouthparts, feeds a lot, commonly aggregate in large masses that generate a lot of heat

  • Crop - Food storage organ in the foregut, can be seen clearly on maggots in third instar

• Puparial Stage - Enters a non-feeding/wandering stage and leaves body to look for a site to pupate where it won’t be disturbed (ex. carpet, soil, hair/clothing of corpse)

  • May leave site altogether

  • Inside puparium (like a chrysalis) pupa changes into an adult fly

  • After emerging from pupa, dries wings for a few hours, flies away; Cycle is now complete

• Once fly is dry and can fly, it cannot be linked back to the scene

• Newly emerged larvae and empty puparial cases indicate that flies have been there long enough to complete at least one full life cycle

• To estimate time of death with blowfly development, you must know:

  • Oldest stage of blow fly associated with the body to identify how far the life cycle has progressed

  • Species of insect - Each species develops at a different rate; Normally identified by morphological/physical features, can be done by DNA

  • Temperature data - Bodies may be far enough away from any weather stations that their weather information may not be relevant; Recommended to track weather in that area for a few weeks and compare it to that of the weather station to see if it is reasonable

  • Developmental data - Must know the rate of development of the species in question

• Other environmental conditions may affect development (ex. if predators are nearby, they may eat larvae for a while, making it seem like colonization occurred later than it did)

• Sequence of insects that colonize a body depends on the nutritional changes in the body and the geographic region, habitat, season, etc.

• Species present on the body can give clues as to time of death (ex. one species that comes earlier in the decomposition process isn’t there, but another one that comes later is - indicates that body has already passed the initial stages of decomposition, etc.)

• Entomologists generally only provide estimates about time of death, not the actual time of death (only estimate minimum elapsed time since death, normally written “at least ____”)

Other Uses for Insects in Death Investigations

• Sphincter muscles relax during violent death, so body may be covered with excretion

• If body is moved few days after death, insects (blowflies, etc.) on the body will be moved with it to a new environment, indicating to entomologists that the body has been moved because the insects present are not local to the new area

• If body was disturbed after death, may be able to estimate when body was disturbed

• Insects can help locate the position of wounds

  • After severe decomposition, wounds may be difficult to discern on the body

  • If insects are present around natural orifices and not anywhere else, there most likely were no wounds on the body

  • If insects are present somewhere other than natural orifices, there may be a wound there (remember wounds are good sources of liquid protein for blowflies and other insects)

• If insects are present around genital region earlier than insects colonize other regions of the body, it may indicate a wound/semen at the site

  • Note that semen is not necessarily indicative of a rape; it may be the result of consensual, unrelated sexual activity

• If insects are present around genital region at the same time or later than insects colonized other regions of the body, it may just be due to normal insect colonization (the genital region still counts as a natural orifice)

• Suspects may unknowingly take entomological evidence with them from a scene, linking them to the scene

• Carrion insects feed on the tissues of the dead body, so they also consume the toxins contained in the body at the time of death, including poison and drugs

• Metabolites - Components of poisons/drugs that occur when they are metabolized

• When an insect eats the flesh of a dead human, it is also eating the toxins in its body, preserving them in the body and serving as a toxicological record of the insect

  • Analyzing the contents of an insect’s stomach can tell us what drugs were present in the human, but not the amount

• Drugs can also affect the development and metabolism of an insect, which must be considered when using them as an estimate for time of death

• DNA can be used to identify an insect in instances where it may not be easy to do so by observing their morphology

• When maggots ingest tissue, the food is stored in the crop before later being digested and utilized

  • This is where tissues containing the victim’s DNA can be found

• Blood-feeding insects can also be analyzed for victim’s DNA

  • Ex. Mosquitoes, bed bugs, fleas

  • Fleas excrete partially digested blood in their frass (feces) in order to feed their young who live on the ground

• Myiasis - The infestation of living human or other vertebrate animals with dipiteran larvae

  • Maggots are attracted to dead, necrotic, unclean skin, regardless of whether or not the person is living or not

  • Can transfer diseases if they feed on a dead animal and then land on a living one (more common with blood-feeding insects like mosquitoes)

• Maggots on living people can provide information on the length of time the person has been neglected

• Myiasis normally occurs with people that are incapable or unwilling to take care of themselves

  • Ex. Children/elderly that rely on someone else for their care, bed sores and dirty diapers can attract insects

  • Ex. Drug/alcohol users who are consistently too intoxicated to take care of themselves

• Cocaine is corrosive - When snorted, it can erode the delicate tissue in the nostrils, destroying the nasal septum, and the person can eventually end up with a single open area that can be infested

• All areas the person may have been able to go to should be searched in case there are insects in later stages of development that can affect the estimate of length of neglect

• When a dead body decomposes, it is only attractive to blowflies for a short period of time

• Blowflies are constantly attracted to a living body, so multiple generations of blowflies can live on a living person

• Maggot Debridement Therapy (MDT) - Using maggots to clean wounds and clear necrotic skin

• Started by Dr. William Baer after observing maggot-infested soldiers during WWI

  • Brought the practice back to the US, used it on children with osteomyelitis (bone condition that almost always required amputation), was successful

  • MDT was replaced by antibiotics

  • Brought back by Dr. Ronald Sherman, who noted that maggots remove necrotic tissue and pus and secrete antibiotics and allantoin, which is good at healing tissue

  • Maggots in a wound stimulate natural granulation (tissue regrowth)

  • Maggots excretions contains ammonia, which alkalinizes the wound, preventing bacteria from infecting it

  • MDT is commonly practiced worldwide

The Use of Insects in Investigating Wildlife or Pet Animal Crimes

• Insects will also infest dead animals, forensic entomology can be applied here as well

• The exact same methods for calculating time of death with humans are applied to forensic entomology with animals

• Can be useful in cases where there are seasons where it is legal/illegal to hunt a certain animal

• Can be useful in animal cruelty cases

• Can be used to determine if a carcass was moved (which is common with wildlife cases)

• Can be used to determine the presence/location of wounds

• Can be used to identify if an animal was poisoned

  • The poisons used to kill animals are often so powerful that other animals that feed on the carcass (ex. scavengers) can also die from it

• Myiasis is much more common in animals than in humans

Challenges to Forensic Entomology

• Temperature plays a huge role in insect development, but the temperature of the scene at the time of death is generally not known, so it has to be extrapolated from weather station data, etc.

  • Both macro and microclimatic factors must be taken into account

• Insects are seasonal, so forensic entomology is only valuable during spring, summer, and fall in temperate climates and all year-round in tropical climates

• If a body is frozen, insect colonization will be delayed until after it thaws

• Wrapping/burying a body can delay colonization, but hardly ever blocks it fully

DNA Typing

• Colin Pitchfork - First criminal to be caught using DNA evidence

• The haploid human genome in gametes contains around 3 billion base pairs (bp)

• The DNA sequences that code for proteins are only around 3% of all DNA

• STRs are about 50% of DNA

• Microsatellite Repeats - A simple class of short tandem repeats (STRs) that consist of 2-7 bp in each unit

• The exact length of these repeats is highly variable, depends on what’s inherited from parents

• Techniques like restriction fragment length polymorphism (RFLP) and STR analysis can be used to estimate the lengths of these variable number tandem repeats (VNTRs)

• Nucleic acid is normally extracted from blood, semen, hair, bone, dried skin

• Nucleases - Enzymes that are responsible for most of the environmental breakdown of DNA

  • Found nearly everywhere

• Many degradative processes require DNA to be hydrated; DNA that is not in a solution lasts longer

• Proteinases - Enzymes that break down proteins

  • Most commonly used is Protein K

  • Used to release DNA from cellular components by breaking down their proteins

• This video literally explains the entire section on PCR in the textbook, so watch it and understand how it works (skip to 10:39 for the explanation, but you should watch the whole thing cuz its cool :D)

• Steps of PCR (in a nutshell):

  • Denaturing - Separating the strands

  • Annealing - Adding the primers

  • Extension - Adding the bases

• PCR only requires sections less then 1000 bases in length; good for degraded samples

• Purpose of STRs is not yet fully known; suspected that it may be to provide chromosomal scaffolding/structure

• STRs normally consist of tetramers (tetranucleotides): 4 bases that are repeated as an array

• Capillary Electrophoresis - Allows for fast and automated methods for genetic profiling with the use of a small capillary

  • DNA is detected with laser-induced fluorescence (LIF)

  • Amplicons (copied sections of DNA) labeled with one of 4 fluorescent dyes

  • Sample injected into capillary, which has a positive charge at one end, negative charge at the other

  • Amplicons separate based on relative size and charge

  • At end of column, amplicons pass by a small window illuminated with a laser, which causes the dyes to fluoresce, creating a color-coded signal

• Mitochondrial DNA (mtDNA) - DNA in the mitochondria

  • Maternally inherited

  • Can be used to establish lineage from the maternal side

  • mtDNA mutates at a much higher rate than that of nuclear DNA

  • Polymorphism - Variation in DNA segments/genes

  • mtDNA is small, but some regions are hypervariable, meaning they are very polymorphic

  • 3 main polymorphic regions in mtDNA (HVI, HVII, HVIII)

• Y-STRs - STRs found specifically on the Y chromosome; useful for identifying DNA from males only, or establishing the presence of a male, etc.

  • Can be used if few sperm are detected in sample, when rapist has had a vasectomy or is sterile, when previous STRs show no Y signal at the amelogenin (gender) locus, when differential extraction is unsuccessful, when there are multiple semen donors, when ratio of female to male DNA is so large that the female DNA masks the male DNA

Forensic Toxicology

• Two categories of forensic toxicology: postmortem drug testing (to find out why someone died) and workplace drug testing (random drug tests to check if employees are using drugs)

Drugs in the Body

• Drugs are tracked in the body with a framework called ADME - absorption, distribution, metabolism, excretion

• Drugs are metabolized primarily in the liver

Drug and Poison Classes

• Most Common Types of Toxicological Samples:

  • Blood - Concentration of toxin in blood correlates more closely with lethal outcome than concentrations in other specimens; most important in forensic toxicology

    • Preferred in DUI cases

  • Urine - Preferred in workplace/sports testing because it’s not invasive; Correlation between the drug concentration in the urine and drug effects is usually poor

  • Gastric Contents - Can be beneficial in case of sudden death of person with large quantities of lethal agent in stomach; If death is a suicide, large amounts of drugs in the stomach can help confirm this

  • Vitreous Humor - Resistant to postmortem decay, used only in postmortem examinations

  • Bile and Liver - Likely to contain significant quantities of most drugs and can sometimes allow for identification of the drug even if it can’t be found in the blood; Bile drains from the liver and is rich is certain types of drugs (ex. opiates)

  • Breath - Relationship exists between alcohol in bloodstream and alcohol in the lung; Concentration of blood alcohol is about 2100 times greater than the concentration of breath alcohol

• Opiates - Class of drugs distinguished by their ability to cause profound euphoria and relieve pain

  • Ex. Codeine

  • Many are derived from/related to morphine (comes from opium poppy, plant that grows in Southeast Asia and other areas of the world)

  • Heroin is an opiate that is easily derived from morphine and is less polar (more fat soluble) than morphine

    • Allows heroin to readily enter the nervous system

  • Studies/research ongoing to find more effective, less addictive alternatives to morphine

  • Semisynthetic opiates are made by a modification of the morphine/codeine molecule

    • Includes hydromorphone, hydrocodone, oxymorphone, oxycodone

    • OxyContin is a sustained form of oxycodone, very dangerous

  • Fentanyl is also a synthetic opiate

  • Depressants - Drugs that produce reduced muscle activity, depressed respiration/heartbeat, inclination to sleep

    • Ex. Opioids

    • Normally cause death in overdoses by paralysis of the respiratory center (slow down heart rate too much)

• Amphetamines - Stimulants that create an excitatory condition characterized by elevations of heart rate, blood pressure, respiratory rate

  • Provokes intense euphoria

  • Methamphetamine (meth) can by synthesized starting with ephedrine

  • Governments recently passed legislation to prevent illicit production of methamphetamines

  • Many compounds that resemble amphetamine include decongestant, anti-insomniac, anorexic medication

    • Sale of these compounds is permitted because they are noticeable less addictive than normal amphetamines

    • Include ephedrine, phenylephrine, phenmetrazine

  • Ephedrine and pseudophedrine commonly used as starting chemicals (precursors) for synthesis of methamphetamines

  • Many states have controls to limit purchases of these drugs

• Cocaine - Stimulant that resembles amphetamine in its abuse potential and pharmacological responses

  • Natural product of the coca leaf (Erythroxylon coca), grows in damp, mountainous regions, especially Andes range of South America

  • Cocaine is alkaline in nature, and is usually extracted with hydrochloric acid, so the substance produced is cocaine hydrochloride

  • Hydrochloric acid is bonded to the nitrogen atom of cocaine

  • Cocaine hydrochloride can be treated with a base and extracted into an organic solvent (ex. ether), creating “free base” or “crack” cocaine

  • Crack cocaine/free base are chemically the same, names refer to slightly different methods of preparation

  • Free base, crack cocaine have much lower boiling points than cocaine hydrochloride

    • Allows for cocaine to be smoked

  • When a drug is smoked, the large surface area of the lung makes it so much more of the drug is absorbed in a smaller amount of time, resulting in a greater drug experience

  • Free base, crack cocaine introduced to the US in the 1980s

  • Cocaine in the blood is metabolized to methylecgonine

  • Benzoylecgonine can also be found but is not the result of metabolism

  • Benzoylecgonine is more commonly tested for in urine tests because cocaine itself is only present in urine in small amounts and for a brief period of time

  • Benzoylecgonine appears in large quantities, is usually present for around three days after cocaine use

  • Toxic amount generally considered > 1 mg/L

• Cannabinoids - Psychoactive compounds that come from the Cannabis sativa plant

  • Ex. Marijuana

  • Tetrahydrocannabinol (THC) - Major active agent in cannabinoids

    • Is present to the extent of 2-6% by weight in cannabis

  • An oily extract of the plant, hashish has much higher THC content (12%), produces much greater psychoactive responses when used

  • Most users smoke hand-rolled cigarettes that contain 75 mg of THC

    • Equals a bioavailability (the extent to which a substance/drug becomes completely available to its intended biological destination) of 2-20%

    • Rapidly absorbed into the blood, reaches peak concentration 10-20 minutes later

    • Produces a drug state that typically lasts around 2 hours

  • Marijuana drug state characterized by euphoria, perceptive alterations, memory impairment

  • Mood swings, hallucinations possible with moderate intoxication

  • Heavy usage may provoke delusions, paranoia

  • Metabolism of THC:

    • THC

    • 11-OH-THC (11-hydroxy-tetrahydrocannabinoic acid), active compound

    • 9-carboxy-THC, major urinary metabolite, inactive compound

      • Can be present in urine as long as 2 months after discontinuation of heavy usage, commonly tested in urine tests

• Prescription and over-the-counter medications can also be deadly when used in excessive amounts at once or when multiple drugs are combined together

• May occur by accident or because of suicide

• Deaths are increasingly involving mixtures of drugs, known as polypharmacy

• Diazepam = Valium

• Zolpidem = Ambien

Nonmedicinal Agents

• Ethanol - Beverage alcohol

• Methanol, isopropanol also present in environment/workplace and can cause injury/death

• Alcohols enter the membranes of nerve cells to disrupt their function

  • Disrupts nerve-to-nerve signaling, resulting in the behavioral effects of alcohol

• Alcohols can be injurious because of the toxic properties of their metabolites

• Methanol → formaldehyde (poisonous), formic acid

  • Treatment of methanol overdose is best accomplished by preventing the conversion of methanol into its metabolites

• Beverage alcohol enters blood mainly from small intestine

• Within the liver, about 90% of ethanol is converted into acetaldehyde and acetic acid, the rest is eliminated via sweat/urine

• Blood level peaks 90 minutes after ethanol ingestion

• Volume of Distribution Equation - Predicts the relationship between blood concentration and alcohol dosage:

Cp\left(\frac{g}{L}\right)=\frac{D\left(g\right)}{\left\lbrack Vd\left(\frac{L}{\operatorname{kg}}\right)\cdot W\left(kg\right)\right\rbrack}

• Cp = Blood concentration, D = dose, Vd = Volume of distribution (0.70 in men, 0.60 in women), W = body weight in kilograms

• General rule - One 12-ounce beer/one cocktail (1.5 ounces of 100-proof alcohol) raises the blood concentration of an average size individual by 0.02%

• Average rate of ethanol clearance from our blood is one drink per hour

• Legal BAC limit in US = 0.08%

• Individual’s handling of alcohol depends on many factors: weight, experience drinking, drinks taken, etc.

• Alcohol contributes to numerous disorders as a results of chronic abuse

• Liver is vulnerable with alcohol abuse, since it metabolizes alcohol

  • Shows pathological response to alcohol ranging from fatty accumulation up to liver cancer

• Brain may be attacked with injuries like several psychosis-like syndromes

• Gas Chromatography - Method used to obtain BAC

  • Blood is the preferred specimen

• Alcohol concentrations of greater than 250 mg/dL can cause death

• Cyanide - Toxic substance that is present in nature

• Hydrogen cyanide gas is the fastest acting, but sodium cyanide salts are highly poisonous but have a slower onset

• Acetonitrile, amygdalin, linamarin metabolize to form cyanide in the body

• Cyanide binds to ferric ions in the cytochrome oxidase (enzyme in the electron transport chain in mitochondria), preventing ATP formation leading to death

• Inhalation of large amounts of hydrogen cyanide are fatal in less than 1 minute

• Cyanide antidote contains nitrite, which oxidizes hemoglobin to methemoglobin, which acts a sink for cyanide, forming cyanomethemoglobin (a much less toxic form of cyanide than cytochrome oxidase)

• Can test for cyanide in whole blood

  • Normal level < 40 ng/mL

  • Levels > 1000 ng/mL associated with stupor

  • Levels > 2500 ng/mL usually fatal

• Carbon monoxide binds hemoglobin much tighter than oxygen, so hemoglobin is unable to fulfill its normal function of transporting oxygen to tissue

• People whose blood carboxyhemoglobin (carbon monoxide binded to hemoglobin) levels exceed 60% are at great risk of death

• If testing is delayed, carboxyhemoglobin levels will underestimate the degree to which someone was exposed to CO because the body starts getting rid of it right after removal from the source

Analytical Methods in Forensic Toxicology

• Most labs attempt to prove a toxin from two sources and two locations (blood and urine, blood and liver, etc.)

• Most tests followed by a confirmatory test to confirm results

• Immunoassay - Tests in which antibodies are used

  • Antibodies are used because they enable the reagents to react only with a substance that recognizes the antibody

  • Antigens found on the surface of red blood cells, antibodies to these antigens found in the serum

  • In an immunoassay, an antibody is prepared against an analyte (substance whose chemical components are being measured) like morphine or methampthemine

• One method of immunoassays that rely on the idea of antigens binding to antibodies is based on chemiluminescence (same process luminol is based on)

• Immunoassays are objective, specific, compatible with automation

• Lack of 100% specificity

• Chromatography - Means of separating chemicals

• Thin Layer Chromatography (TLC) - Specimen is extracted into an organic solvent and spotted onto a glass plate coated with silica

  • Plate is placed in a tank that contains a mobile phase that migrates up the plate (like how paper towel draws up water)

  • Solvent moves up the plate, carrying sample molecules

  • The more sample molecules interact with the solid silica gel on the plate, the less the compounds move, while compounds that do not interact much will move quickly

  • Allows for separation of compounds in sample

  • Once solvent reaches top of plate, let dry

  • Drugs on the plate can be identified based on how far they traveled and the colors they produce with various identifying reagents

  • Inexpensive

• Gas Chromatography - Confirmation test paired with mass spectrometry for ultimate specificity and accuracy

  • Thin tube called the column coated in a very thin layer of the stationary phase (analogous to the silica gel in TLC)

  • Sample prepared by dissolving it in a solvent (ex. methanol), pulled into a syringe

  • Sample injected into a heated entrance port to the column, where the sample turns into gas and mixes with the inert gas in the column (serves as the mobile phase, analogous to the solute in TLC

  • Based on the properties of the molecules in the gas, different molecules will have different interactions with the stationary phase and will thus exit the column at different times

  • A detector at the end of the column detects the time it takes for different molecules to exit (called retention time), these are compared to other retention times of known substances to identify the substance

  • Often paired with mass spectrometry for better specificity

• GC-MS - Collective name for a gas chromatography and mass spectrometer unit together

• Mass Spectrometer - Provides specific identifcation of a substance

  • Most common - Quadrupole mass filter

  • Gas coming from GC column is introduced to a region under vaccuum (low pressure is important to prevent collisions between ions created by the instrument and atmospheric components)

  • Sample molecule is ionized to form charged components

  • The M+ ion is called the “molecular ion” because it strips away a single electron from the original compound, so it will have the same molecular weight as the parent molecule

  • Many different ionization techniques, most common is electron impact (EI) where ions are created by the substance under study by electrons

  • Short lived molecular fragments are formed, recorded, quantified, creating something like a fingeprint of the substance allowing for its identification

  • Subsequent mass spectra compared with spectra of known substances

• Sometimes mass spectra are not unique, and extra testing is required

• National Institute of Standards and Technology (NIST) has a library of over 140,000 compounds that can be searched for mass spectra matches

• Liquid Chromatography - Mass Spectrometry (LC-MS) - Technology used where liquid chromatograph replaces the gas chromatograph used in GC-MS

• Sample mixture under study swept into a liquid solvent instead of a gaseous stream, carried to a detector

  • Because the chemical does not have to be heated, this works with virtually every known organic chemical

  • GC-MS cannot be used with 80% of organic chemicals because either the substance being tested is thermolabile (breaks down at elevated temperature) or hydrophilic

• LC-MS is expensive

• Tandem Mass Spectrometers - Instruments that combine LC with multiple mass spectrometers in series

  • Also represented as MS^n, where n is the number of MS units in the instrument

• Many labs are replacing GC-MS with LC-MS^n

• Capable of detecting very small amounts of drugs and metabolites in biological matrices

Metal Analyses

• Lead, mercury, arsenic, cadmium - very toxic metals

• Colorimetric testing - Allows for accurate measurement of metals

• Marsh Test - One of the first and most famous color-based tests for arsenic

• Metal assays based on photometry have high detection limits

• Needs a large specimen size (ex. one procedure for arsenic testing calls for a 5-mL sample size)

• Inductively Coupled - Mass Spectrometry (ICP-MS) - Best and newest technique for metal analysis

  • Expensive and pretty new

  • Argon atoms in an ICP-MS torch are subjected to radiofrequency that makes them collide, raising the temperature of the torch to > 6000 C

  • Atoms in the specimen are ionized, directed to a mass detector where they can be separated on the basis of their masses and charges

  • Certain masses and charges of isotopes of certain metals are very similar to those of other elements, causing ambiguity

Interpreting Drug Findings

• Toxicokinetics/Pharmacokinetics - How drugs/poisons move through the body

• Toxicogenomics/Pharmacogenomics - Describes how genetic factors play a role in toxicity of an ingested drug/poison

  • Metabolism of drugs requires enzymes that come in different forms across different people based on genetics

  • Different enzymes affect how fast the drug is metabolized and thus excreted from the body

• In the workplace, to determine if a potential employee is a drug addict, urine samples are tested

• In the case of an employee whose behavior has suddenly become noticeably sporadic/unusual, blood test will be done

• Limit for drugs is above zero because some metabolites can appear if merely exposed to drug (ex. if someone was smoking marijuana near you, marijuana metabolites that are lower than the confirmation threshold can appear in the urine)

• To determine if death was caused by a toxin, appropriate quantities of the toxin must be present, other findings (ex. congestion in the lungs) must be consistent with this finding, no other apparent cause of death must be present

• Impossible to state that a specific death was not poison related, because that would mean you tested every single possible poison, which is impossible

• Not very many experiments regarding toxic levels of drugs in humans, so the data over that can have shortcomings

• Most experiments over it done on animals, but they may have different reactions to different amounts of toxins

  • Ex. Dioxin is relatively harmless to humans, but the LD50 (quantity that kills 50% of a population) in guinea pigs is 0.6 micrograms/kg; In dogs, it is 200 fold greater than that amount

• Postmortem Redistribution - The concentration changes that occur after death as drugs move from one region of the body to another

  • Ex. If drug is lipophilic, it may leave the bloodstream and absorb into fat cells after death

• In lethal injections (for the death penalty), the following procedure is used:

  • Injection of sodium thiopental to render person unconscious quickly

  • Injection of pancuronium - muscle relaxant that causes paralysis

  • Injection of potassium chloride - stop the heart from beating