Crime Labs and Their Roles

Crime Labs and Their Roles

• U.S. crime labs are rapidly expanding and often overwhelmed with drug cases, leading to backlogs, including unanalyzed rape kits.

Federal Crime Labs

• FBI: Maintains the world's largest crime lab with broad investigative powers.
• DEA: Analyzes seized drugs.
• ATF: Focuses on alcohol, tobacco, firearms, and explosives.
• US Postal Service: Investigates crimes associated with the U.S. Postal Service.

State Crime Labs

• State crime labs operate under central state authority, providing forensic services to most areas of the state.
• These labs work closely with local law enforcement agencies, offering specialized forensic services.

Local Crime Labs

• Local crime labs serve county and city agencies, often financed locally.
• The size of local crime labs can vary, with some being as large as state labs.

Basic Services in Crime Labs

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

What Forensic Scientists Do

• Forensic scientists apply principles and techniques from the physical and natural sciences to analyze evidence during criminal investigations.
• They provide expert testimony in court, explaining the significance of findings and methodologies.
• Forensic scientists testify about their findings, methodologies, and analysis in criminal cases.

Scientific Method

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

Legal Precedents and Courtroom Cases

• Crawford v. Washington: Addresses the Confrontation Clause of the Sixth Amendment, ensuring a defendant's right to confront witnesses.
• Melendez-Díaz v. Massachusetts: Establishes that forensic scientists must appear in court to testify regarding their findings.
• Frye v. United States: States that scientific evidence must be generally accepted by the scientific community to be admissible in court (Frye Standard).

Daubert v. Merrell Dow Pharmaceuticals

• Establishes guidelines for judges regarding scientific evidence admissibility including:
  • Testing: Has the theory or technique been tested?
  • Peer Review: Has it been published and peer-reviewed?
  • Error Rate: Does the technique have a known error rate?
  • Standards: Are there established standards?
  • Acceptance: Is the method widely accepted by the scientific community?

Evidence Collection and Handling

• Evidence Technicians (CSI): CSI personnel are often on call to collect evidence from crime scenes, ensuring proper recognition and processing.

Crime Scene Procedures

• Secure the Scene: Secure the crime scene with tape and boundaries to prevent contamination or tampering.
• Crime Scene Walkthrough: Conduct a walkthrough identifying entry/exit points and locating obvious evidence.

Search Patterns

• Line/Strip Search: One or two investigators follow straight parallel lines to search for evidence.
• Grid Search: Two investigators conduct a thorough overlapping search pattern.
• Spiral Search: Conducted in a spiral pattern either from the center outward or from the boundary inward.

Evidence Collection

• Proper evidence packaging is critical to prevent contamination.
  • Use separate containers for each item of evidence.
  • Use manila envelopes, screw-cap vials, or pill boxes to store evidence.
  • Biological materials should be air-dried and stored in paper envelopes or paper bags to prevent moisture buildup.
  • DNA evidence (e.g., blood, semen, saliva) should be stored carefully to avoid contamination.

Chain of Custody

• Record everyone who has handled the evidence and its location at all times.
• Properly maintaining the chain of custody ensures evidence remains untampered and is admissible in court.
• Procedure:
  • Evidence must be labeled, marked, and logged in evidence submission forms.
  • Accountability: Every person who handles the evidence must be accounted for.

Contamination and Prevention

• Sources of Contamination: Coughing, sneezing, or improper handling can introduce foreign DNA or materials onto evidence.
• Prevention Measures:
  • Use PPE, such as latex gloves, facemasks, coveralls, and shoe covers, reduces contamination risk.
  • Disposable gloves and equipment should be used to avoid contaminating evidence.

Famous Forensic Case: Amanda Knox

• Amanda Knox was wrongfully convicted of the murder of Meredith Kercher in Italy and was initially charged with murder, sexual assault, and slander.
• Evidence: The alleged weapon, a knife, had DNA from both Knox and Kercher; however, experts later challenged these findings.
• Forensic evidence mainly pointed to Rudy Guede, who had fingerprints in Kercher's bedroom.
• Media Influence: The media sensationalized Knox's personal life, calling her "Foxy Knoxy" and painting her as a party-loving suspect.
• Outcome: Knox was initially convicted, retried, and finally exonerated by the Italian Supreme Court based on insufficient forensic evidence linking her to the crime.

Types of Physical Evidence

• Blood: Can be used to determine whether a crime has occurred.
• Hair and Fibers: Trace evidence that can link a suspect or victim to a crime scene.
• Semen: Often found in cases involving sexual assault.
• Documents: Includes checks, letters, or other written items that may provide evidence.
• Drugs and Explosives: Evidence often found in drug-related or terrorist crimes.
• Firearms and Ammunition: Often analyzed for ballistic matching.
• Paint, Plastic, Rubber: Used in cases involving vehicles or other manufactured items.

Identification vs. Comparison

• Identification: Determines the physical or chemical identity of a substance like identifying a drug type.
• Comparison: Compares the suspect's evidence with a reference sample to establish if they come from the same source.

Class vs. Individual Characteristics

• Class Characteristics: Evidence linked to a group such as fibers or paint from a common source.
• Individual Characteristics: Unique features traced to a specific individual or source such as fingerprints, DNA.

Forensic Databases

• IAFIS: National database for fingerprint and criminal history information.
• CODIS: DNA database for exchanging and comparing DNA profiles.
• NIBIN: Database to compare ballistics evidence (firearm markings).
• PDQ: Forensic database containing information on automobile paint and its chemical composition.

Chapter One Questions

• Forensic science: the application of science to law.
• Sherlock Holmes: fictional character that excited the imagination of forensic scientists and criminal investigators.
• Alphonse Bertillon: devised the first system of personal identification using body measurements.
• Francis Galton: developed the first statistical study proving the uniqueness of fingerprints.
• Leone Lattes: devised the first workable procedure for typing dried bloodstains.
• Calvin Goddard: made the comparison microscope an indispensable tool of firearms examination.
• Albert S. Osborn: associated with early efforts at applying scientific principles to document examination.
• Hans Gross: advocated the application of science to criminal investigation.
• Edmond Locard: formed one of the first functional crime laboratories in Lyons, France.
• Locard's Exchange Principle: the transfer of evidence that occurs when two objects come in contact.
• Los Angeles Police Department: created the first forensic laboratory in the United States in 1923.
• California: an excellent example of a state with an integrated system of regional/satellite laboratories.
• Britain's crime laboratory system: characterized by a national system of government-funded laboratories.
• Increasing demand for DNA analyses: the single most important factor in the expansion of crime laboratory services in the U.S.
• Four federal agencies offering forensic services: FBI, DEA, ATF, and U.S. Postal Inspection Service.
• Decentralized system of crime laboratories in the United States: exists at the federal, state, county, and municipal levels.
• Physical science unit: applies chemistry, physics, and geology to identify and compare crime-scene evidence.
• Biology unit: examines blood, hairs, fibers, and botanical materials.
• Firearms unit: examines bullets, cartridge cases, shotgun shells, and ammunition.
• Toxicology unit: examines body fluids and organs for drugs and poisons.
• Crime scene investigation unit: dispatches personnel to retrieve evidence for lab examination.
• Frye v. United States: set forth the "general acceptance" principle for judicial admissibility of scientific evidence.
• Daubert v. Merrell Dow Pharmaceuticals, Inc.: Supreme Court ruled that judges don't have to rely solely on "general acceptance." -Kumho Tire Co., Ltd. v. Carmichael: extended the "gatekeeping" role of a trial judge to all expert testimony, not just scientific testimony.
• Coppolino v. State: a Florida case that exemplifies the trial judge's flexibility and discretion in matters of scientific inquiry.
• Expert witness: can demonstrate a particular skill or knowledge to help the court determine the truth. The expert witness's courtroom demeanor may play an essential role in the court's assignment of weight to testimony.
• The expert witness's testimony incorporates their personal opinion relating to a matter studied or examined.
• Proper investigator recognition and collection of crime-scene evidence depends on training from the crime laboratory.
• Crawford v. Washington: U.S. Supreme Court addressed issues relating to the Confrontation Clause of the Sixth Amendment in 2004.
• Melendez-Diaz v. Massachusetts: U.S. Supreme Court addressed the use of affidavits instead of in-person testimony by forensic examiners in 2009.

Evidence Collection Examples

• White powder found at a crime scene goes to the Drug Unit to test for controlled substances.
• A bloodstained shirt goes to the Biology Unit to analyze blood type and DNA.
• Bullet casings from a shooting scene go to the Firearms Unit to match to weapons and determine caliber.
• Questioned documents like a forged check go to the Document Examination Unit.
• A vial containing body fluids for poison testing goes to the Toxicology Unit.
• A fingerprint lifted from a doorknob goes to the Latent Fingerprinting Unit.
• Skull fragments found at a site go to the Anthropology Unit.
• A hard drive seized from a suspect's computer goes to the Forensic Computer and Digital Analysis Unit.
• Soil samples from a suspect's shoe go to the Criminalistics (Physical Science) Unit.
• Strands of hair found on a victim go to the Biology Unit.
• Glass fragments from a broken window at a burglary go to the Criminalistics (Physical Science) Unit.
• A pill bottle with unknown pills goes to the Drug Unit
• A cell phone used in cyberstalking goes to the Forensic Computer and Digital Analysis Unit.

Chapter Two Information

• Physical evidence encompasses all objects that can establish or disprove whether a crime was committed or link a crime, victim, or perpetrator.
• Scientific evaluation of crime-scene evidence cannot usually overcome the results of a conducted criminal investigation.
• Collection of physical evidence requires a highly skilled individual specializing in this area of investigation.
• Unauthorized personnel must be excluded from crime scenes.
• Failure to protect a crime scene properly may result in the destruction or altering of evidence.
• The first officer arriving on the scene is responsible for preserving and protecting the area, relying on their training.
• First priority at a crime scene: obtaining medical assistance and minimizing disturbance of evidence.
• Crime scene tape, rope, or traffic cones should encompass only the center of the scene where the crime occurred.
• An accurate log must be kept of who enters and exits the scene and when.
• The lead investigator will not immediately proceed to gain an overview of the situation and develop a strategy.
• Three methods for recording the crime scene: photography, notes, and sketches.
• Note-taking begins with the call to a crime-scene investigator.
• Crime-scene notes should include a precise record of personnel movements, starting with the first officer on scene.
• Crime-scene notes should not be written from memory back at the laboratory.
• Located evidence must be fully described in the investigator's notes before collection. Observation and recording of the state of an injured or deceased victim is important and must be done.
• Most important prerequisite for photographing a crime scene: maintaining it in an unaltered condition.
• Photographs of physical evidence: must include overviews as well as close-ups.
• Value of crime-scene photographs: showing the layout, witness positions, and relationships of people in the scene.
• Most commonly used camera for crime-scene photography: single-lens reflex (SLR).
• Digital camera captures light on a light-sensitive sensor.
• Each crime scene should be photographed as completely as possible, including the area where the crime took place and adjacent areas where important acts occurred.
• Succession of photographs: overview first, close-up last.
• Overview photographs: include only points of entry and points of exit.
• Many jurisdictions have developed protocols for the use of digital photography to avoid enhancement or doctoring.

Sketching the Crime Scene

• Sketching combines notes and photography.
• Unlike the rough sketch, the finished sketch is constructed with care and concern for aesthetic appearance and must be drawn to scale.
• Computer-aided design (CAD) programs provide an extensive symbol library and may create a three-dimensional sketch.
• An investigator needs only draw a rough sketch at the crime scene to outline dimensions and critical objects.
• A detailed, systematic search of the crime scene for physical evidence is necessary.
• Crime-scene search is undertaken to locate physical evidence.
• Search patterns for evidence: line pattern, grid pattern, polar coordinate pattern, and spiral pattern.
• Failure to recognize physical evidence or to properly preserve it inhibits laboratory examination.
• Besides obvious items of physical evidence, possible carriers of trace evidence must be collected for detailed examination.
• Trace evidence should never be removed from the object bearing it if possible.
• Each item collected at the crime scene must be placed in a separate container.
• An ordinary mailing envelope is not considered a general-purpose evidence container.
• An airtight container is not recommended for bloodstained garments.
• Items of clothing are to be air-dried before packaging.
• Charred debris from an arson scene is not best placed in a porous container.
• Chain of custody must be established with respect to the possession and location of physical evidence.
• Most physical evidence requires submission of standard/reference material for comparison.
• The Supreme Court restricted warrantless searches at homicide scenes in Mincey v. Arizona.
• The Supreme Court dealt with search-and-seizure procedures at an arson scene in Michigan v. Tyler.

Chapter Three Information

• Identification: determines a substance's physical or chemical identity with as near absolute certainty as existing analytical techniques will permit.
• The number and type of tests: must sufficiently exclude all other substances from consideration.
• Comparative analysis: subjects a suspect specimen and a standard/reference specimen to the same tests to find a connection.
• Frequency: the rate of occurrence of an event.
• Individual characteristics: trace evidence to a common source with an extremely high degree of probability.
• Class characteristics: evidence associated with a group and not with a single source.
• One of the deficiencies of forensic science: the inability to assign exact probability values to comparisons of most class physical evidence.
• The value of class physical evidence: corroborating events with data free of human error and bias.
• The weight accorded physical evidence during a trial: left entirely to the trier of fact.
• Reliability on personal experience: For the most forensic scientists must rely upon with personal experience when interpreting significance of class physical evidence.
• Eyewitness accounts, confessions, and informant testimony can be disputed.
• Physical evidence can exclude or exonerate a person from suspicion of committing a crime.
• The distinction between individual and class evidence is not always easy to make.
• Failure to take proper safeguards may unfairly prejudice a case against the suspect.
• Studying forensic science texts is no substitute for practical experience.
• Sensitivity: Modern analytical techniques have become so sensitive that the forensic examiner must be aware of the natural variations among materials when interpreting the significance of comparative data.
• Fingerprint can not be positively identified through the IAFIS database, must be done visually by an expert.
• DNA profiling can be done through CODIS
• The NIBIN database: allows firearm analysts to compare markings made by firearms on bullets recovered from crime scenes.
• Automotive paints: contained in the PDQ database