chapters 5 (death investigation), 6 (fingerprints), 8 (the microscope), and 9 (firearms, tool marks, & other impressions)

Scene Investigation

• preliminary reconstruction of events that precede the onset of death, so all significant details of the scene can be recorded

• blood spatter & blood flow patterns must be documented

• tire marks or shoe prints documented

• fingerprints processed & collected

• evidence that’s discarded, dropped, or cast off are collected

• weapons, fired bullets, & castings are collected & documented

• photographs must always be taken before the scene is altered

Autopsy

• the examination of a body after death

  • goal of a forensic/medico-legal autopsy is to determine the course of death & confirm the manner of death, often used in proceedings

Evidence From the Autopsy

• medical examiner or coroner will examine the victim to establish a cause & manner of death

• tissues & organs may be retained for pathological & toxicological examination

• following items may be collected:

  • clothing

  • fingernail scrapings

  • combings from head & pubic hairs

  • buccal (inside of cheek) swab for DNA

  • vaginal, anal, & oral swabs (sex related crimes)

  • recovered bullets

  • hand swab or any areas suspected of being in contact with DNA (touch or saliva)

External Examination

• broad overview of the condition of the body & the clothing

  • classifying injuries that includes distinguishing types of wounds

Internal Examination

• dissecting the human body generally entails remaining all internal organs through Y-shaped incision beginning at the top of the shoulder & extending down to the pubic bone

  • entails weighing, dissecting, & sectioning of each organ

Toxicology

• the internal examination is also where toxicological specimens are taken that includes blood samples, stomach content, bile, & urine

  • blood = alcohol & drugs

  • some drugs redistribute or re-enter blood after death & complicates the interpretation of postmortem blood

Common causes of death…

• blunt-force injury

• sharp-force injury

• asphyxia

• gunshot wound

• substance abuse

Blunt-force Injury

• caused by non-sharpened object (bats or pipes)

  • can abrade tissue, forming a laceration, or can cause a contusion (bruising) due to tiny ruptured blood vessels bleeding beneath the skin

Sharp-force Injury

• occur from weapons with sharp edges (knives or blades)

  • weapons that are capable of cutting or stabbing

Asphyxia

• variety of conditions that involve interference with the intake of oxygen

  • hanging

  • strangulation

  • death at a fire scene is caused primarily by carbon monoxide

Gunshot Wounds

• projectiles that are fired by a firearm

  • the distance a weapon was fired is one of the most important factors for characterizing gunshot wounds

Substance Abuse

• forensic pathologists will routinely order toxicological tests for the presence of drugs in nearly all investigations

  • can directly cause death or complications that contribute to death

Manner of Death

• relates to the circumstances that led to the fatal result

• classified into five categories:

  1. homicide

  2. suicide

  3. accidental

  4. natural

  5. undetermined

Homicide

non-accidental death resulting from grossly negligent, reckless, or intentional acts of another person

Suicide

an individual taking his or her own life

Accidental

no intent to cause harm through gross negligence on the part of a perpetrator or the victim

Natural

death from disease, environmental abuse, or age

Undetermined

a rational classification that can’t be established

Estimating Time of Death

• pathologist can never give an exact time of death, but approximation includes…

  • algor mortis

  • livor mortis

  • rigor mortis

• can determine the amount of potassium in the vitreous humor can be used to approximate time of death

• stomach contents may reveal the deceased’s last meal; extent of digestion can help determine time of death

• preceding methods won’t work when decomposition sets in

Algor Mortis

• process in which a body adjusts to equalize with the environments temperature

  • generally body loses heat by 1-1.5 degrees per hour until the body reaches the environmental temp, but this can be affected by body size, clothing, etc.

Livor Mortis

• results in the setting of blood in areas of the body closest to the ground

  • process begins 20 min to 3 hrs after death & continues up to 16 hrs

  • different lividity patterns in a body indicates that the body was moved, but before livor mortis full fixed

Rigor Mortis

• results in the shortening of muscle tissue & the stiffening of body parts in the position of death

  • typically occurs within the first 24 hrs & disappears after 36 hrs

Recovering & Processing Remains

• sites where human remains are found must be treated like a crime scene

  • secured & thoroughly searched to locate all bones if they’re scattered or other aspects of evidence such as discarded items or footwear impressions

  • must be documented & collected

Forensic Anthropology

• concerned primarily with the identification & examination of human skeletal remains

  • bones can determine a person’s sex, approximate age, race, & possible skeletal injuries

• when determing the sex the size & shape of the pelvis & skull are looked at…

  • pelvis

    • wide, circular pelvic opening & short, wide nature of sacrum = female

    • more longer & narrow = male

  • skull

    • smaller size with less pronounced features = female

    • larger size with more pronounced brow bone = male

Forensic Entomolgy

• study of insects & their relation to a criminal investigation, commonly used to estimate time of death

  • by determining the most developed stage of fly found on a body, entomologists approximate the postmortem interval (PMI)

  • can also go off of sequence of arrival

• not always straightforward because stage development is affected by environmental influences (location, climate, weather, drugs, etc.)

Alphonse Bertillion

French police expert who devised the first systematic attempt at personal identification

Bertillion System

relied on a detailed description of the subject, combined with full length & profile photographs & a system of precise body measurements called anthropomety

Will West and William West

• in 1903 the Bertillion System couldn’t distinguish between two men, & fingerprinting was able to distinguish them

  • New York City civil service commission in 1901, & training of American police by Scotland Yard representatives at the 1904 World’s Fair began to use fingerprinting

Francis Galton

• published textbook Finger Prints in 1892

• the British government adopted fingerprinting as a supplement to the British system

  • next step was the creation of classification systems capable of filing many thousands of prints in a logical & searchable sequence

Dr. Juan Vucetich

devised a classification system that’s stil used in most spanish speaking countries

Fingerprint Principles

• fingerprints are a reproduction of friction skin ridges found on the palm side of the fingers & thumbs

• principles include:

  1. a fingerprint is an individual characteristic because no two fingerprints have yet to be found to possess identical ridge characteristics

  2. fingerprint will remain unchanged during an individual’s lifetime

  3. fingerprints have general ridge patterns that permit them to be systematically classified

Principle One: a fingerprint is an individual characteristic because no two fingerprints have yet to be found to possess identical

• probability of existence of two identical fingerprints is small (Galton calculated a possible existence of 64 billion)

• doesn’t matter of shape or pattern, but the ridge characteristics, known as minutiae

  • bifurcations, ridge endings, & enclosures

  • as many as 150 minutiae on the average finger

• in the U.S. there’s no predetermined minimum number of friction ridge characters that must be established to have a positive identification

  • point-by-point comparison to prove identity

Principle Two: fingerprint will remain unchanged during an individual’s lifetime

• Epidermis: outer layer of the skin, & determines the inner layer of skin

• Dermal Papillae: layer of cells between the epidermis & dermis; responsible for determining the form & pattern of the ridges on the surface of the skin

  • each ridge is populated with pores leading to sweat glands, from which perspiration is deposited to the skin

• once the finger touches a surface, perspiration (& oils that may have been picked up by touching hairy portions of the body) is transferred onto that surface, leaving the finger’s ridge pattern (fingerprint)

  • prints deposited in this manner are invisible to the eye & are commonly referred to as latent fingerprints

Principle Three: fingerprints have general ridge patterns that permit them to be systematically classified

• all fingerprints are divided into either a loop, arch, or whorls (L.A.W.)

• 60-65% of population have loops, 30-35% have whorls, & about 5% have arches

Loops

• must have one or more ridges entering form one side of the print, recurving, & exiting from the same side

  • Ulnar loop: opens towards the little finger

  • Radical loop: opens towards the thumb

• type lines: two diverging ridges that surround the pattern area

• delta: ridge point at or nearest to the point where two type lines diverge; all loops must have a delta

• core: approximate center of the loop pattern

Whorls

• divided into four groups:

  1. Plain

  2. Central Pocket Loop

  3. Double Loop

  4. Accidental

• all whorl patterns have type lines & a minimum of two deltas

Plain Whorl & Central Pocket Loop

• have at least one ridge that makes a complete circuit

  • if an imaginary line drawn between the two deltas within these patterns touches any of the circular ridge, the pattern is plain

  • if no such ridge is touched, the pattern is a central pocket loop

Double Loop

made up of two loops combined into one fingerprint

Accidental

contains two or more patterns, or is a pattern not covered by the other categories

Arches

• least common of the three general patterns, & are divided into two distinct groups:

  1. Plain arches: formed by ridges entering from one side of the print, rising & falling, & exiting on the opposite side (like a wave)

  2. Tented arches: similar to plain arch except that instead of rising smoothly at the center, there’s a sharp upthrust or spike, or the ridges meet at an angle that’s less than 90 degrees

• arches don’t have type lines, deltas, or cores

ACE-V

• four step process to identify & individualize a finger print

  1. Analysis: identify points of comparison & external factors

  2. Comparison: compare the questioned print at 3 levels…

     • encompasses the general ridge flow & pattern configuration

     • inculdes lecating & comparing ridge characteristics or minutiae

     • includes examination & locations of ridge pores, breaks, creases, scars, & other permanent minutiae

  3. Evaluation: determine a conclusion

  4. Verification: the examiner’s conclusion is confirmed by a second examiner

AFIS (Automated Fingerprint Identification System)

• ability of a computer to scan & digitally encode fingerprints so they can be subject to high-speed computer processing

• software incompatibilities often means that slat * local AFIS systems can’t communicate with each other & share info

• 2014, FBI integrated its IAFIS (Integrated Automated Fingerprint Identification System) into the NGI (Next Generation Identification)

Latent Prints

• once a finger touches a surface, body perspiration &/or oils present on the finger ridges are transferred to that surface, leaving an impression

Visible Prints

• made when fingers touch a surface after the ridges have been in contact with a colored material such as blood, paint, grease, or ink

• plastic prints: ridge impressions left on soft material such as putty, wax, soap, or dust

Developing Latent Prints

• prints developed on hard & nonabsorbant surfaces (ex., glass, mirror, tile, & painted wood) are preferably developed by applying powder

• prints on porous surfaces (ex., paper, cardboard, & cloth) generally require chemical treatment

Nonporous Surfaces

• powders are available in a variety of different colors, most common are black carbon & aluminum dust

• Super Glue is approximately 98-99% cyanoacrylate ester, a chemical that actually interacts with & visualizes a latent print

  • can be accomplished by using a fuming chamber (for up to 6 hrs) or a hand held want that heats a cartridge containing cyanoacrylate

Detecting Prints on Porous Surfaces

1. Iodine Fuming

   • heating iodine crystals that cause vapors which combine with latent prints to make them visible

   • not permanent & will fade, making it necessary to photograph

2. Ninhydrin

   • reacts with trace amounts of amino acids present in latent prints to produce a purple-blue color

   • method of choice for porous surfaces

3. Physical developer

   • silver nitrate based reogent used to develop prints when other methose are ineffective

   • useful for developing prints on porous objects that ma have been wet at one point

Mincroscope

optical instrument that uses a lens or combination of lenses to magnify & resolve fine details of an object

Virtual Image

the magnified image seen by looking through a lens

Real Image

an image viewed directly

Compound Microscope

• object to be magnified is placed under the lower lens (objective lens) & the magnified image is viewed through the upper lens (eyepiece lens)

  • magnification can be calculated by multiplying the magnifying power of the objective lens times the power of the eyepiece

• Mechanical system…

  • base: the support

  • arm: c-shaped upright structure

  • stage: plate on which the specimens are placed

  • body tube: hollow tube on which the objective & eyepiece lenses are mounted

  • coarse adjustment: knob used to focus the microscope lenses by moving the body

  • fine adjustment: knob used to focus the lenses by moving the body tube, but by a much smaller magnitude

• Optical system…

  • illuminator: artificial light

    1. transmitted illumination: when the light is directed up through the specimen from the base

    2. vertical/reflected illumination: when light comes from above & reflects off the specimen

  • condenser: lens system under the microscope stage that focuses light onto the specimen

  • objective lens: lens closest to specimen

  • parafocal: microscope is focused with one objective in place

  • eyepiece/ocular lens: lens closest to the eye

    1. monocular: having only one eyepiece

    2. binocular: having two eyepieces

Comparison Microscope

• consists of two independent objective lenses joined together by an optical bridge to a common eyepiece lens

  • when looking through the eyepiece, the objects are observed side-by-side

  • firearm examination began with this microscope

Stereoscopic Microscope

• two monocular compound microscopes properly spaced & aligned to present a 3D image of a specimen

  • useful for evidence not requiring high magnification

  • large working distance is great for big, bulky items

Polarizing Microscopy

• light that’s confined to a single plane of vibration is said to be plane-polarized

  • has found wide applications for the study of birefringent materials (materials that can split a beam of light in two, each with their own refractive index value)

  • refractive index data helps identify minerals present in soil samples or identifying man-made fibers

Microspectrophotometer

• a spectrophotometer coupled with a light microscope

  • can simultaneously obtain visible absorption spectrum or IR spectrum of the observed material

  • useful for trace evidence, plant fiber, & ink evidence

Scanning Electron Microscope (SEM)

• bombards a specimen with a beam of electrons instead of light to produce a highly magnified image from 100x to 1,000,000x

  • depth of focus is 300 times better than optical systems

  • electrons normally produce X-ray emissions that can be used to characterize elements present in materials

Primer Residue on Hands

• firing a weapon propels residues towards a target, but also blows gunpowder & primer residues back towards the shooter

• scanning electron microscopes allow examiners to measure the amount of barium & antimony on a suspects hand (thumb web, back of hand, & palm

Forensic Palynology

• the collection & examination of pollen & spores connected with crime scenes, illegal activities, or terrorism

  • link a suspect to crime scene or victim

  • prove or disprove alibi

  • include or exclude suspects

  • track previous whereabouts of item or suspect

  • indicate the geographical origin of some items

Firearm Identification

discipline mainly concerned with determining whether a bullet or cartridge was fired by a weapon

Handguns

• fires one round at a time

  • Revolvers: several firing chambers within a revolving cylinder

    • swing-out

    • break-top

    • solid frame

  • Semi-automatic pistols

    • removable magazine

    • one shot per trigger pull

Long Guns

• may be single-shot, repeating, semi-automatic, or automatic

  • Shotguns

    • ammunition (shell) contains numerous ball-shaped projectiles called slug

    • narrowing of the smooth barrel (choke of the shotgun) can concentrate shot when fired

  • Rifles

    • barrel with lands & grooves

    • bullet ammunition is impressed with lands & grooves during firing

Gun Barrel Markings

• inner surface of gun’s barrel leaves markings on bullet passing through it

• manufacture of a barrel also requires impressing its inner surface with spiral grooves, a step known as rifling

  1. cutting all grooves in one pass with a cutter (broach)

  2. pressing all grooves at once onto the barrel with a button

  3. hummer forging the barrel using a mandrel containing the reverse image of the rifling

• surface of original bore remaining between the grooves are called lands

  • guide the bullet through the barrel with spin for accuracy

• diameter of a gun barrel, measured between opposite lands, known as caliber

Striations

fine lines found in the interior of the barrel

Bullet Examination

• no two rifled barrels will have identical striation markings

  • comparison of bullets can eliminate possibilities when there’s differences in class characteristics

Shotguns

• smooth barrel

• generally fire small lead balls/pellets that aren’t impressed

• diameter of a shotgun barrel is expressed by the term gauge

• the higher the gauge number, the smaller the barrel diameter

Firing a Weapon

• pulling a trigger releases the weapons firing pin that strikes the primer which ignites the powder

• expanding gases from burning gunpowder propels bullet forward through barrel, pushing cartridge case or shell back with equal amount of force against the breechface

Cartridge Comparison

firing pin, breechface, & extractor after individualization

NIBIN (National Integrated Ballistics Information Network)

• produces database files from bullets & cartridge casings retrieved from crime-scenes (often linking weapon to a crime)

• ultimate decision for final comparison is determined by a forensic examiner through microscopic methods

Distance Determination

• if muzzle of a weapon was close enough, unburned & partially burned particles of gunpowder will be deposited onto the target

• distribution of gunpowder & other discharge around a bullet hole allows a distance assessment

• precise distance is determined by comparing powder-residue pattern located on victim’s clothing or skin against test patterns made with suspected weapon fired at various distances form a target

Star-shaped (stellate) tear patterns

weapon is held in contact with or less than 1 inch from target

Halo of vaporous lead (smoke)

normally 12 to 18 inches or less

Scattered specks of unburned & partially burned powder grains

distances of 25 inches & occasionally 36 inches

Bullet Wipe

• fired more than 3 ft.

• usually won’t deposit any powder residue

• only indication is a dark ring around the hole

Gunpowder Residue

• distance determination involving shotguns is related to weapon & ammunition

• muzzle-to-target distance is estimated by measuring the spread of the discharged shot

  • as shot distance increases, pellets progressively separate & spread out

Greiss Test

chemical test that detects gunpowder residue that aren’t visible

Primer Residue on Hands

• firing weapon propels residues towards target & gunpowder & primer back towards the shooter

  • looks for amount of barium & antimony on thumb web, back of hand, & palm

  • may characterize morphology of particles containing these elements to determine whether or not a person fired, handled, or near a discharged firearm

Serial Numbers

• criminalist is required to restore a serial number when it has been removed or obliterated by grinding, rifling, or punching

• restoration is possible with chemical etching because metal crystals in the stamped zone are placed under a permanent strain that extends a short distance beneath the original numbers

Firearm Evidence Collection

• collected by holding weapon by edge of trigger guard or by checkered portions of the grip

• weapon gets unloaded is most cases

• revolver’s chambers, position, & corresponding cartridges must be recorded

  • marked for identification (usually on tag or trigger guard) & chain of custody established

• avoid obliterating striation markings on the bullet

  • wrap in tissue paper before placing in a pill box or envelope

Tool Markings

• any impression, cut, gouge, or abrasion caused by a tool coming into contact with another object

  • comparison microscope is used to compare crime-scene tool marks with test impressions

• under no circumstance must a crime-scene investigator attempt to fit the suspect tool into the tool mark

Other Impressions

• when shoes & tire marks are present preservation is best accomplished by photographing & casting

• if impression is easily recoverable such as glass, paper, or floor tile, transport evidence

Points of Comparison

• sufficient number of points of comparison or uniqueness of such points will support a finding that both questioned & test impressions originated from only one source

• computer software & websites assist in making shoe print & tire impression comparison

• bite mark impressions on skin & food are important evidence in homicide & rape cases