Crime Labs: Roles and Functions

Crime Labs and Their Roles

• Rapid expansion of U.S. crime labs is occurring with the increased number of drug cases and unanalyzed rape kits.

Federal Crime Labs

• FBI maintains the largest crime lab, with broad investigative powers.
• DEA analyzes seized drugs.
• ATF focuses on alcohol, tobacco, firearms, and explosives.
• The U.S. Postal Service investigates crimes associated with mail.

State and Local Crime Labs

• Operate under central state authority and provide forensic services to the majority of areas within the state.
• Serve county and city agencies, often locally government funded.

Basic Crime Lab Units

• Physical Science Unit: Uses principles of physics, geology, and chemistry to identify and compare evidence such as soil, glass, or chemicals.
• Biology Unit: Investigates biological evidence including body fluids, hair, and fibers.
• Document Unit: Handles handwriting analysis and examines questioned documents like checks and wills.
• Photography Unit: Records and examines physical evidence through photography and documents crime scenes.
• Firearm Unit: Investigates bullets, cartridge cases, shotgun shells, and ammunition.
• Toxicology Unit: Examines body fluids and organs for drugs or poisons.
• Latent Fingerprint Unit: Processes and analyzes latent fingerprints.
• Polygraph Unit: Conducts lie detector tests for investigations.

Forensic Scientists

• Apply scientific principles to analyze evidence during criminal investigations and provide expert testimony in court.

Scientific Method

• A question is formulated that is important for the investigation.
• A hypothesis is created that answers the question.
• Experiments are done to test the hypothesis.
• If testing validates a hypothesis, this becomes evidence.

Legal Precedents and Courtroom Cases

• Crawford v. Washington addresses a defendant's right to confront witnesses per the Sixth Amendment.
• Melendez-Díaz v. Massachusetts requires forensic scientists to testify in court.
• Scientific evidence must be generally accepted by the established community to be admissible in court, per Frye v. United States.
• Daubert v. Merrell Dow Pharmaceuticals establishes guidelines for judges regarding scientific evidence admissibility

Daubert Guidelines

• Testing: Has the theory been tested?
• Peer Review: Has it been published and reviewed?
• Error Rate: Does it have a known error rate?
• Standards: Are there standards controlling the procedure?
• Acceptance: Is the method widely accepted?

Evidence Collection

• Evidence Technicians/CSI personnel are on-call to collect evidence and ensure proper processing.
• A crime scene must be secured with crime tape and boundaries, and a walkthrough is conducted to locate entry/exit points and evidence.

Search Patterns

• Line/Strip Search: Investigators follow straight, parallel lines.
• Grid Search: Investigators conduct an overlapping search pattern.
• Spiral Search: Search is in a spiral, from the center outwards.

Evidence Collection

• Proper packaging is critical to prevent contamination by using separate containers, manila envelopes, or pill boxes.
• Biological materials should be air-dried and stored in paper envelopes.

Chain of Custody

• A record of everyone who has handled the evidence and where it has been, ensuring evidence remains untampered and admissible
• Evidence labelled, marked, and logged in evidence submission forms.

Contamination Prevention

• Coughing, sneezing, or improper handling introduces materials onto evidence, and PPE (latex gloves/facemasks) and disposable equipment reduces this risk.

Amanda Knox Case

• Amanda Knox was wrongfully convicted of the murder of Meredith Kercher in Italy.
• Forensic evidence mainly pointed to Rudy Guede, who had fingerprints in Kercher's bedroom
• The media sensationalized Knox's personal life, portraying her negatively.
• Her initial conviction was overturned by the Italian Supreme Court due to insufficient forensic evidence.

Types of Physical Evidence

• Blood evidence helps determine if a crime has occurred.
• Hair and fibers are trace evidence linking people to a scene.
• Semen is often found in assaults.
• Documents includes checks, letters, or other written items as evidence.
• Drugs and explosives are evidence in drug-related/terrorist crimes.
• Paint, plastic, and rubber are often linked to vehicle incidents.
• Firearms and Ammunition are used for ballistic matching.

Identification vs. Comparison

• Identification determines the identity of a substance (e.g., identifying a drug).
• Comparison determines if a suspect sample and a reference sample share a common origin.

Classes vs. Individual Characteristics

• Class Characteristics: Linked to a group (fibers/paint from a source).
• Individual Characteristics: Traced to an individual (fingerprints, DNA).

Forensic Databases

• IAFIS: Fingerprint and criminal history information.
• CODIS: DNA profiles for comparison.
• NIBIN: Ballistics evidence from firearms.
• PDQ: Chemical data for automobile paint.

Key Figures

• Bertillon: Devised a system for personal identification using body measurements.
• Galton: Developed the first statistical study proving the uniqueness of fingerprints.
• Lattes: Devised the first procedure for typing dried bloodstains.
• Goddard: Made the comparison microscope an indispensable tool of firearms examination.
• Osborn: Applied scientific principles to document examination.
• Gross: Advocated for the application of science to criminal investigation.
• Locard: Suggested that the transfer of evidence occurs when two objects come in contact with one another (Locard's Exchange Principle).

History

• The first functional crime lab was in Lyons, France, under Edmond Locard.
• The first forensic laboratory in the United States was created in 1923 by the Los Angeles Police Department.
• A system of integrated, regional and satellite laboratories operates in the state of California.
• Britain's crime laboratory system is characterized by a national system of government-funded laboratories
• Increased demand for DNA analyses has been the single most important factor in expanding crime laboratory services in the United States

Federal Agencies

• The FBI, DEA, ATF, and the U.S. Postal Inspection Service all offer important services related to forensic science
• A decentralized system of crime laboratories exists in the United States under various governmental agencies at the federal, state, county, and municipal levels.

Crime Lab Functions

• The physical science unit identifies and compares crime-scene evidence by using chemistry, physics, and geology.
• The biology unit examines blood, hairs, fibers, and botanical materials
• The firearms unit investigates bullets, cartridge cases, shotgun shells, and ammunition.
• The toxicology unit examines body fluids and organs for drugs and poisons.
• The crime scene investigation unit dispatches trained personnel to retrieve evidence.
• The "general acceptance" principle as a criterion for the judicial admissibility of scientific evidence was set forth in Frye v. United States.
• Regarding assessment of admissibility of new/unique scientific tests, the trial judge does not need to rely solely on "general acceptance", per Daubert v. Merrell Dow Pharmaceuticals, Inc.
• An expert witness can demonstrate a skill or knowledge in a trade or profession that helps the court determine the matter at issue.
• U.S. Supreme Court addressed issues relating to the Confrontation Clause of the Sixth Amendment in the case of Crawford v. Washington
• The expert witness's courtroom demeanor may play an important role in deciding what weight the court assigns to their testimony.
• Personal opinion counts as testimony from an expert witness if they studied or examined a case.

Procedures

• Drug Unit tests for controlled substances
• Biology Unit analyzes blood type, DNA, etc. on bloodstained shirts
• Firearms Unit matches bullet casings shot from a scene to weapons and determine caliber
• Document Examination Unit analyzes writing and can check the authenticity of documents like a check.
• Toxicology Unit tests a vial of bodily fluids for drugs, alcohol, or poisons.
• Latent Fingerprinting uses the AFIS databases to determine the identidy of unknown prints found at the scene
• Anhtropology Unit can help in forensic science by being able to identify if human remains exist and may be able to dtermine the trauma
• Soil samples or strands of hair may be found at the scene to find the cause with the crime scene and what may have taken plave