Crime Labs: Types & Functions

Crime Labs: An Overview

• Crime labs in the U.S. are increasing rapidly, often burdened with drug-related cases and rape kit backlogs.

Federal Crime Labs

• FBI: Has the world's largest crime lab and broad investigative powers
• DEA: Focuses on analyzing seized drugs
• ATF: Concentrates on alcohol, tobacco, firearms, and explosives
• US Postal Service: Deals with crimes related to the postal service

State and Local Crime Labs

• State labs operate under state authority, offering forensic services across the state while collaborating with local law enforcement
• Local labs serve city and county agencies, with funding from local governments

Basic Crime Lab Units

• Physical Science Unit: Uses physics, geology, and chemistry to analyze evidence like soil, glass, and chemicals.
• Biology Unit: Analyzes biological evidence (body fluids, hair, fibers, etc.).
• Document Unit: Handles handwriting analysis and investigates questioned documents
• Photography Unit: Records and examines physical evidence using photography, documenting crime scenes for analysis
• Firearm Unit: Analyzes bullets, cartridge cases, shotgun shells, and ammunition.

Optional Forensic Lab Services

• Toxicology Unit: Detects drugs or poisons in body fluids and organs
• Latent Fingerprint Unit: Processes and analyzes latent fingerprints from crime scenes
• Polygraph Unit: Conducts lie detector tests

Forensic Scientists and Their Role

• Apply scientific principles to analyze evidence in criminal investigations
• Provide expert testimony, offering specialized knowledge in court

Scientific Method in Forensics

• Question: Develop an investigation-related question
• Hypothesis: Formulate a reasonable hypothesis to answer the question
• Experiment: Conduct experiments to test the hypothesis
• Validation: Validate the hypothesis through testing to obtain scientifically validated evidence

Legal Precedents and Courtroom Cases

• Crawford v. Washington: Addresses the Sixth Amendment's Confrontation Clause regarding a defendant's right to confront witnesses
• Melendez-Díaz v. Massachusetts: Requires forensic scientists to testify in court about their findings
• Frye v. United States: Scientific evidence must be generally accepted in the scientific community to be admissible
• Daubert v. Merrell Dow Pharmaceuticals: Establishes guidelines for judges on scientific evidence admissibility, including testing, peer review, error rate, standards, and acceptance

Evidence Collection and Handling

• CSI personnel collect evidence from crime scenes, ensuring proper recognition and processing
• Crime Scene Procedures include securing the scene, establishing boundaries, and conducting scene walkthroughs to locate evidence
• Line/Strip, Grid, and Spiral are different search patterns employed to find evidence

Evidence Collection Guidelines

• Package each item of evidence separately
• Use appropriate containers like manila envelopes, screw-cap vials, or pill boxes
• Air-dry biological materials and store them in paper to prevent moisture buildup
• Handle DNA evidence carefully to avoid contamination

Chain of Custody

• Record of everyone who handled the evidence and its location at all times
• Proper maintenance ensures evidence remains untampered and admissible in court
• Procedure involves labeling, marking, and logging evidence
• Accountability tracks every person who handles the evidence

Contamination Prevention

• Contamination can occur through coughing, sneezing, or improper handling, introducing foreign DNA or materials
• Prevention involves using PPE like gloves, masks, coveralls, and shoe covers

Case Study: Amanda Knox

• Amanda Knox was wrongfully convicted of murder in Italy, with the media sensationalizing the case
• Forensic evidence primarily pointed to Rudy Guede, leading to Knox's exoneration

Types of Physical Evidence

• Blood, hair, fibers, semen, documents, drugs, explosives, firearms, ammunition, paint, plastic, and rubber are types of physical evidence

Identification vs. Comparison

• Identification determines a substance's physical or chemical identity
• Comparison compares a suspect's evidence to a reference sample

Class vs. Individual Characteristics

• Class characteristics link evidence to a group
• Individual characteristics trace evidence to a specific individual or source

Forensic Databases

• Francis: Fingerprints
• IAFIS: National fingerprint and criminal history database
• CODIS: DNA profile database
• NIBIN: Ballistics evidence database
• PDQ: Automotive paint information database

Key Figures in Forensic Science History

• Alphonse Bertillon: Devised a system of personal identification using body measurements
• Francis Galton: Developed the first statistical study proving fingerprint uniqueness
• Leone Lattes: Created the first workable procedure for typing dried bloodstains
• Calvin Goddard: Made the comparison microscope indispensable for firearms examination
• Albert S. Osborn: Applied scientific principles to document examination
• Hans Gross: Advocated applying science to criminal investigation
• Edmond Locard: Established one of the first functional crime laboratories and advocated the Locard's Exchange Principle

Crime Lab Systems

• United States: Decentralized system with federal, state, county, and municipal labs
• Britain: National system of government-funded laboratories

Admissibility of Scientific Evidence

• Frye v. United States: Established the "general acceptance" principle
• Daubert v. Merrell Dow Pharmaceuticals: Set guidelines for judges regarding scientific evidence admissibility

Expert Witnesses

• Demonstrate a particular skill or knowledge to help the court determine the truth
• Courtroom demeanor can impact how the court weighs their testimony
• Their testimony may include personal opinions related to studied or examined matters

Crime Scene Evidence

• Recognized and collected based on training from the crime laboratory

Legal Cases Impacting Forensic Science

• Crawford v. Washington: Addressed the Confrontation Clause of the Sixth Amendment
• Melendez-Diaz v. Massachusetts: Addressed the practice of using affidavits instead of in-person testimony from forensic examiners

Crime Scene Documentation

These document the crime scene effectively: White powder in cases, bloodstained shirts are tested in Biology Unit. Bullet casings and questioned documents analyzed as well, vials for poisons tested and fingerprint also units in forensic are analyzed within the forensic labs.