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

DNA Profiling

• With the use of polymerase chain reactions (PCR), trace samples of DNA evidence can be amplified (copied) so that adequate amounts of DNA evidence are available for testing

• Amplifying will amplify contamination as well, so proper handling of DNA evidence is important

• Keep DNA evidence dry and cool and away from direct sunlight/warm conditions

• Polymorphisms - Regions of high variability in DNA that can be used to distinguish one person from another

• DNA fingerprinting/profiling examine regions of high variability to establish the identity of a person

• DNA is isolated and cut using restriction enzymes, creating fragments of DNA called restriction fragments

• Restriction fragments separated via gel electrophoresis, radioactive probes bind to highly variable regions, creating a unique band pattern that can be used to identify people

• Gel electrophoresis has been replaced by the use of STR analysis, which analyzes shorter regions of DNA

• Short Tandem Repeats (STRs) are short sequences of repeating bases (normally less than 50)

• Can be more easily recovered from DNA found in evidence

• FBI uses 13 core STRs for identification of Americans

• An individual’s DNA STR profile is unique

• Allele Frequency - A calculation of how often a particular allele appears within a given population

  • Equals (# of times an allele is observed in a given population)/(total alleles observed in the population)

• Alleles for 8 repeats for the STR marker TH01 is more common among blacks and least common among Hispanics

• Y STRs (STRs on the Y chromosome) are used to trace male ancestry because only males carry the Y chromosome, so they are passed down directly

• mtDNA (mitochondrial DNA) is used to trace maternal ancestry because only mothers pass on mitochondrial DNA