Crime Labs: Federal, State, and Local Roles

Crime Labs and Their Roles

• Crime labs in the U.S. are rapidly expanding, often overwhelmed with drug-related cases and facing backlogs of unanalyzed rape kits.

Federal Crime Labs

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

State Crime Labs

• State crime labs operate under central state authority, providing forensic services to most areas and collaborate with local law enforcement agencies.

Local Crime Labs

• Local crime labs serve county and city agencies, often financed by local governments.
• Depending on the respective area, these labs can be as large as state labs.

Basic Services in Crime Labs

• The Physical Science Unit uses physics, geology, and chemistry to compare evidence like soil, glass, or chemicals.
• The Biology Unit investigates biological evidence such as body fluids, hair, fibers.
• The Document Unit handles handwriting analysis and investigates questioned documents like checks, signature, and wills.
• The Photography Unit records and examines physical evidence through photography, documenting crime scenes and evidence for analysis.
• The Firearm Unit investigates evidence such as discharged bullets, cartridge cases, shotgun shells, and ammunition.

Optional Services in Forensic Labs

• The Toxicology Unit examines body fluids and organs to detect drugs or poisons.
• The Latent Fingerprint Unit processes and analyzes latent fingerprints left at crime scenes.
• The Polygraph Unit conducts lie detector tests for investigations.

Role of Forensic Scientists

• Forensic scientists apply scientific principles and techniques to analyze evidence during criminal investigations and provide expert testimony in court to explain findings.

Scientific Method

• Formulate a Question: Develop a question important for the investigation.
• Formulate a Hypothesis: Create a reasonable hypothesis to answer the question.
• Test the Hypothesis: Conduct experiments to test the hypothesis.
• Validate the Hypothesis: If the hypothesis holds true after testing, it becomes scientifically validated evidence.

Legal Precedents and Courtroom Cases

• Crawford v. Washington: Addresses the Confrontation Clause of the Sixth Amendment.
• Melendez-Díaz v. Massachusetts: Forensic scientists are required to appear in court to testify regarding their findings.
• Frye v. United States: Scientific evidence must be generally accepted by the scientific community to be admissible in court.
• Daubert v. Merrell Dow Pharmaceuticals: Establishes guidelines for judges regarding scientific evidence admissibility.

Daubert Guidelines for Scientific Evidence Admissibility:

• Testing: The theory/technique must undergo testing.
• Peer Review: Peer review and publication are essential.
• Error Rate: Technique must have known error rate.
• Standards: Established standards are essential.
• Acceptance: Widespread acceptance is necessary.

Evidence Collection and Handling

• Evidence Technicians (CSI): They collect evidence from crime scenes, ensuring proper recognition and processing.

Crime Scene Procedures:

• In order to avoid contamination or tampering, secure crime scene with crime scene tape.
• Identify entry/exit points and locate obvious evidence to conduct a crime scene walkthrough.

Search Patterns:

• Line/Strip Search: Investigators search by following straight, parallel lines.
• Grid Search: Investigators conduct an overlapping search pattern.
• Spiral Search: Conducted in a spiral pattern either from the center outward or the boundary inwards.

Evidence Collection

• Use separate containers for each item properly package evidence to prevent contamination
• Manila envelopes, screw-cap vials, or pill boxes are typically used to store evidence.
• Air-dry biological materials and store in paper envelopes or paper bags to avoid moisture buildup.
• To avoid contamination, DNA evidence such as blood, semen, and saliva should be stored carefully.

Chain of Custody

• The chain of custody is a record of everyone who handled the evidence and where it has been.
• Properly maintaining ensures the integrity of evidence is admissible in court.
• Every person who handles the evidence must be accounted for.
• Evidence must be labeled, marked, and logged in evidence submission forms.

Contamination and Prevention

• Coughing, sneezing, or improper handling can introduce foreign DNA or materials, causing contamination.
• The use of PPE such as latex gloves, facemasks, coveralls, and shoe covers reduces contamination risk.
• Use disposable gloves and equipment to avoid contaminating evidence.

Famous Forensic Case: Amanda Knox

• Amanda Knox Case Overview: She was wrongfully convicted of murdering Meredith Kercher in Italy.
• The media sensationalized Knox's personal life with the nickname "Foxy Knoxy".
• Outcome: Knox was ultimately exonerated due to lacking evidence in the case.

Types of Physical Evidence

• Blood: Used to determine if a crime has occurred.
• Hair and Fibers: Trace evidence linking suspects/victims.
• Semen: Evident in sexual assault cases.
• Documents: Provide written evidence like checks and letters.
• Drugs and Explosives: Linked to drug-related or terrorist crimes.
• Firearms and Ammunition: Analyzed for ballistic matching.
• Paint, Plastic, Rubber: Used in cases involving vehicles or manufacturing.

Identification vs. Comparison

• Identification: Determines physical/chemical identity of a substance.
• Comparison: Compares suspect's evidence with reference samples to see if come from the same source.

Class vs. Individual Characteristics

• Class Characteristics: Linked to a group
• Individual Characteristics: Unique qualities, such as fingerprints or DNA,
• These can be traced to a specific source.

Forensic Databases

• IAFIS: A national database for fingerprints and criminal history information.
• CODIS: A DNA database to compare DNA profiles.
• NIBIN: Database used to compare firearm markings on ballistics evidence.
• PDQ: Database containing chemical information on automobile paint and its composition.

Chapter One Questions

• Using science to law is forensic science.
• Sherlock Holmes inspired forensic scientists and investigators.
• Alphonse Bertillon devised identification using body measurements.
• Francis Galton developed the fingerprint uniqueness study.
• Leone Lattes created the first procedure for typing dried bloodstains.
• Calvin Goddard made the comparison microscope essential for firearms exams.
• Albert S. Osborn applied scientific principles to document examination.
• Edmond Locard advocated science in criminal investigation.
• Edmond Locard advocated transfer of evidence upon object contact and vice versa in Locard's Exchange Principle.
• The first forensic laboratory in the United States was created in 1923.
• The increasing demand for DNA analyses recently and rapidly expanded crime laboratory services in the US.

Chapter Two Questions

• All objects that can establish/disprove crimes linking to victims or perpetrators are physical evidence.
• The first officer arriving on the scene of a crime preserves the area to the greatest extent possible.
• Medical assistance would be a priority at crime scenes while minimizing disturbance of evidence.
• Crime scene sketch combines notes and photography.
• The rough sketch shows the scene's dimensions/objects.
• Investigators draw a rough sketch at crime scene displaying dimensions/relevant objects.
• A systematic crime scent search has to be conducted for physical evidence.
• Besides physical evidence, possible carriers of trace evidence must be collected in the laboratory.
• Proper chains of custody must be established in order for possession of physical evidence.
• In Mincey v. Arizona, the Supreme Court restricted warrantless searches at homicide scenes.
• Michigan v. Tyler dealt with search-and-seizure procedures.

Chapter Three Questions

• Identification process determines the chemical identity of the substance that includes all other substances from consideration.
• Comparative analysis tests suspect and standard specimen to determine similar origin.
• Frequency is the rate of events.
• Individual characteristics can be traced to a common source.
• One major shortcoming is the forensic science examines assign approximate probability values to class physical evidence.
• Criminal evidence can not determine or exclude a person from committing a crime.
• Natural variations become sensitive when one relies among materials when interpreting the significance of comparative data because of Modern analytical techniques.
• The database applies to DNA profiling and is called CODIS
• The database allows ballistic information.
• Automotive paint contains chemical information.