Forensic Science Course Study Guide
Forensic Science Course Study Guide
1. General Information About Forensic Science
Overview
Forensic Science: The application of scientific methods and processes to solve crimes.
Criminalist: A forensic scientist who collects, preserves, and analyzes scientific evidence during the course of an investigation.
Differences between TV Forensics and Real Forensics:
TV Forensics:
Interrogate suspects and kick down doors.
Make judgment calls about guilt/innocence.
Operate independently without permission.
Assume multiple areas of expertise.
Expect quick DNA results (1 day).
Real Forensics:
Do not interrogate suspects; often arrive at scenes long after the crime.
Should not make judgments about guilt or innocence (impairs scientific objectivity).
Work as part of a team under police leadership.
Specialize in specific disciplines.
Average DNA results take 2-3 weeks.
History & Development of Forensic Science
Notable Figures:
Sir Arthur Conan Doyle: Creator of Sherlock Holmes, first to use forensic methods in literature (e.g., fingerprinting, serology).
Mathieu Orfila: Established forensic toxicology in 1814.
Alphonse Bertillon: Developed anthropometry for identification.
Francis Galton: Conducted the first study on fingerprints in 1892.
Leon Lattes: Developed blood group determiner (514).
Hans Gross: Integrated science with police investigation.
Calvin Goddard: Established ballistic identification.
Alberto Osborne: Focused on document examination (1910).
Edmond Locard: Known for the principle of exchange and established the first crime lab.
Evolution of Forensic Labs
Federal Bureau of Investigation (FBI):
Established a national laboratory in 1932 under J. Edgar Hoover.
Largest forensic lab in the world; performs over 1 million examinations yearly.
Crime lab services include toxicology, document examination, photography, evidence collection, etc.
Legal Considerations in Forensics
Frye vs. United States (1923): Established the Frye standard for determining the admissibility of scientific evidence:
Evidence must be “generally accepted” in the relevant scientific community.
Daubert vs. Merrell Dow Pharmaceuticals (1993): Established the reliability of scientific evidence based on:
Testability and peer review status.
Known or potential error rates.
General acceptance in the scientific community.
Expert Witness Testimony
Qualifications:
Education credentials.
Field experience.
Published work.
Membership in professional organizations.
Voir Dire: A process where an expert witness establishes their qualifications in court.
Crime Scene Investigation Basics
Importance of Crime Scenes: Forensic science begins at the crime scene; mistakes are irreversible.
Observational Points in Crime Scene Investigation:
Identify items that are present and those that are absent.
Types of Crime Scenes:
Outdoor: Varies in size, may span miles.
Indoor: Easier to control but crowded.
Conveyance: Related to transport.
Crime Scene Categories:
Primary Crime Scene: Where the crime occurred.
Secondary Crime Scene: Any subsequent location connected to the crime.
Crime Scene Investigation Process
Steps in Crime Scene Processing
Secure and Isolate the Scene: Preserve the integrity of the crime scene.
Conduct a Walk-Through: Assess the scene for safety and initial observations.
Document the Scene:
Photography: Overview and itemized shots, photo logs.
Sketches: Rough and finished; include measurements.
Note-Taking: Precise details and context.
Search for Evidence: Systematic patterns to ensure thorough documentation.
Collect & Package Evidence: Proper methods for collecting; use appropriate materials (paper for most evidence, airtight containers for arson).
Chain of Custody: Documentation of evidence handling.
Safety and Legal Considerations: Ensure legal compliance for searches, including warrants or exigent circumstances.
Documentation Methods
Sketching:
Rough Sketch: Includes measurements and key items.
Final Sketch: Scaled with a clean layout.
Triangulation: Measurement techniques to determine positions in the scene.
Photography: Critical at multiple angles and stages of the investigation, including proper metadata.
Physical Evidence
Definition: Any tangible object that can be collected and analyzed in relation to a crime.
Types of Physical Evidence:
Objects (e.g., weapons, drugs).
Body materials (e.g., blood, tissue).
Impressions (e.g., fingerprints, tire tracks).
Class vs. Individual Characteristics:
Class Characteristics: Shared traits;
Individual Characteristics: Unique details linking evidence to a specific source.
Forensic Databases
IAFIS: National fingerprint identification and criminal history system (FBI).
CODIS: DNA profile comparison system across crime labs.
NIBIN: Links firearm markings found on bullets and cartridge casing.
PDQ: Automotive paint data query for chemical information on paints.
CSI Effect
Prosecutors believe crime programs skew juror’s expectations in court cases.
Negative effects:
Jurors demand hard evidence and are skeptical of circumstantial evidence.
Difficulty finding impartial jurors based on their viewing habits.
Resource strain on investigations for more forensic evidence.
Educating juries results in excessive time for defense lawyers.
Positive effects:
Improved public knowledge of legal processes.
Increased interest in careers within criminal justice.
2. Death Investigation
Overview
Trigger Warning: Sensitive material regarding death.
Common Misconceptions in Death Investigation
Myths include the ability to quickly determine the time of death, recreate death scenes, and conclude hand dominance easily.
Coroner vs. Medical Examiner System
Coroner: Quasi-judicial role without specific training, historically determined cause of death.
Medical Examiner (ME): A qualified medical professional responsible for determining cause and manner of death.
Training:
Medical school, internship, pathology residency, and additional fellowship.
Medicolegal Investigator (MLI):
Minimum qualifications include experience in law enforcement or medical investigation.
Cause & Manner of Death
Cause of Death: Medical determination based on evidence.
Manner of Death: Legal classification (natural, accidental, homicide, suicide, undetermined).
Time of Death: Determined from postmortem interval (PMI).
Methods include rigor mortis (stiffness), algor mortis (temperature), and livor mortis (coloration).
Methods to Establish Time of Death
Rigor Mortis: Signifies muscle stiffness; occurs 6-24 hours post-death.
Algor Mortis: Body temperature decreases, subject to various factors.
Livor Mortis: Settling of blood, dependent on body position; can indicate timing and position at death.
Stages of Human Decomposition
Fresh Stage: When the body appears intact.
Bloated Stage: Gases build-up; expansion occurs 4-10 days post-death.
Decay Stage: Maggot activity, skin breakage, and foul odors.
Post-Decay Stage: Reduction to bones and hair, visible after 20-50 days.
Autopsy Procedures
Purpose and Circumstances:
Sudden or unexplained deaths warrant autopsy.
Steps in Autopsy:
Document prior evidence.
Examine body (height, weight, physical features).
Check under fingernails, especially for signs of foul play.
Internal review of organs and tissues for abnormalities (using incisions for access).
Final report completed by the medical examiner.
Important Medical Terminologies
Asphyxia & Hypoxia: Conditions related to the lack of oxygen.
Injury Classifications: Include bruises, lacerations, and contusions.
3. Forensic Photography
Role of Forensic Photographer
Provides objective, true images of the crime scene for analysis and court use.
Digital Imaging in Forensic Photography
Original images must be preserved; any changes are logged for admissibility.
Depth of Field in Photography
Depth of Field (DOF): Focus range in an image. Critical in crime scene documentation.
Essential Photography Techniques
Important Photographs: Overview, intermediate, and itemized shots;
Photo Log: Essential for recording the metadata of images taken.
Equipment and Tools
Basic components include cameras, lenses, tripods, and lighting tools appropriate for various situations.
4. Fire Investigation
Fire Investigation Basics
Understanding the chemistry and physics involved in fire is critical.
Investigation Focus Areas
Proof of Incendiarism: Evaluating the scene to establish cause.
Proof of Opportunity: Analyzing the accessibility of the area.
Proof of Motive: Investigating financial or emotional motivations for the fire.
Fire Properties and Behaviors
Fire Tetrahedron: Comprises fuel, heat, oxygen, and chemical reaction.
Types of Heat Transfer:
Conduction: Direct contact transfer.
Convection: Movement of liquids and gases.
Radiation: Transmitted without contact.
Key Fire Investigation Definitions
Oxidation: Oxygen combining with substances to create heat.
Exothermic Reaction: Releases energy.
Flashover: A critical temperature where everything flammable ignited.
Collection and Analysis of Fire Evidence
Collect appropriately; label all materials.
Evaluate for potential causes, flames, and smoke patterns to analyze.
5. DNA
Forensic DNA Overview
DNA is a major component in evidence analysis.
Two types of DNA: nuclear and mitochondrial, each with unique properties.
DNA Testing Applications
Applications in paternity testing, missing persons identification, and crime scene analysis.
DNA Profiling Methods
Extraction techniques, quantification procedures, and amplification through Polymerase Chain Reaction (PCR).
Interpretation of DNA Evidence
Analytical processes used to compare DNA profiles from different sources.
6. Fingerprints
General Facts
Fingerprints are unique and remain unchanged after fetal formation.
Types of Fingerprints: Latent, visible, plastic - each needing different analysis techniques.
Identification Methods
Chemical methods include iodine fuming and ninhydrin application for latent prints.
Automatic Identification Systems (AFIS)
Used to compare fingerprints in criminal investigations.
7. Firearms Investigation
Firearm Types & Examinations
Different types of firearms include pistols, shotguns, and rifles; each producing unique ballistic evidence.
Integral Ballistics Investigation Techniques
Methods to determine firing distance, angle, caliber, and operability of firearms.
Evidence Collection Protocols
General principles for handling gunshot evidence and residue recovery.
8. Forensic Entomology
Role in Crime Scene Analysis
Entomological evidence used to determine time of death or locate victims.
Life Stages of Insects in Decomposition
Different species of flies and their behavior indicate the postmortem interval, contributing essential data for investigations.
9. Bloodstain Pattern Analysis
Blood Pattern Significance
Bloodstains reveal crucial information about events during the crime.
Bloodstain Patterns
Bloodstain types include spatter, splashes, and arterial spurts, each indicating different circumstances of the event.
Tools for Analysis
Techniques to trace the origin of the bloodstains and potential victim positioning.
10. Impression Evidence
Importance of Impression Analysis
Impressions can link suspects to crime scenes through various objects.
Types of Impressions
Include shoe tracks, tire marks, tool impressions, etc., requiring different collection methods.
11. Accident Investigation
When is an Accident Investigated?
Factors such as fatalities, injuries, or unusual circumstances indicate a need for thorough analysis.
Skills Required for Accident Investigators
Proficiency in math and physics is crucial for reconstructing the incidents and determining causes.
Important Concepts in Accident Investigation
Using evidence like skid marks, vehicle damage, and eyewitness accounts to piece together the event.
Speed Determination Equation
S = ext{ extbf{speed}} (mph)
D = ext{ extbf{skid distance}}
A = ext{ extbf{acceleration (ft/s^2)}}