Forensic Science Chapter 1 Test Ultimate Study Guide

Case Study: Ted Bundy

  • Background and Criminal Profile: Ted Bundy was a law student who systematically targeted young women across multiple jurisdictions.

  • Escape and Apprehension: Following a conviction for kidnapping in Utah, Bundy escaped from custody. He was subsequently apprehended while driving a stolen motor vehicle.

  • Forensic Evidence and Conviction: Bundy was convicted in part through the analysis and presentation of forensic bite-mark evidence.

  • Execution: Bundy was executed in 1989.

  • Scientific Validity Caveat: Bite-mark evidence has since faced substantial scientific criticism regarding its methodology and dependability, distinguishing its historical forensic application in this case from contemporary views on its forensic reliability.

Fundamentals and Definition of Forensic Science

  • Definition: Forensic science is the application of scientific methods, principles, and techniques to investigate crimes and examine evidence suitable for introduction and evaluation in a court of law.

Historical Development of Forensic Science

  • Early Chinese Case (3rd Century):

    • Investigative Context: A coroner investigated a suspicious death involving a burned body to determine whether an individual died as a result of the fire or was murdered prior to the fire being set.

    • Methodology: The coroner compared the burned remains of two pigs: one pig was burned while alive, and the second was burned after it was already dead.

    • Forensic Observation: The pig burned while alive had accumulated ash inside its mouth and respiratory passages, whereas the pig that was already dead showed no ash inside its mouth.

    • Case Conclusion: This comparative analysis demonstrated that the deceased husband lacked ash in his mouth, indicating that he was likely dead prior to the fire.

  • Anthropometry (1879):

    • Developer: Alphonse Bertillon developed the system in 1879.

    • Definition and Function: A systematic method of personal identification founded on precise, standardized physical body measurements and detailed morphological descriptions.

    • Historical Role: Served as the primary scientific identification system before the universal adoption of fingerprint analysis.

  • Locard's Exchange Principle (1910):

    • Origin: Formulated by Edmond Locard in 1910.

    • Fundamental Premise: Whenever two people or objects come into physical contact with one another, a mutual transfer of material occurs between them, commonly encapsulated by the maxim: "Every contact leaves a trace."

    • Factors Influencing Transfer Extent:

    • Intensity/Pressure: The amount of physical force or pressure applied during contact.

    • Duration: The length of time over which the contact occurs.

    • Nature of Materials/Surfaces: The physical and chemical characteristics, texture, and composition of the interacting surfaces or materials.

Major Breakthroughs and Milestones in Forensic Science

  • Francis Henry Galton (1892):

    • Published foundational, influential research on fingerprint identification.

    • Established unique fingerprint friction ridge patterns as an objective, reliable scientific method for personal identification.

  • Dr. Karl Landsteiner (1901):

    • Discovered the major human ABO blood groups.

    • Provided the scientific foundation for serological blood typing.

  • Dr. Leone Lattes (1915):

    • Devised a functional procedure for determining ABO blood types directly from dried bloodstains, enabling blood typing of physical evidence at crime scenes.

  • Sir Alec Jeffreys (1984):

    • Developed the technique of DNA fingerprinting (DNA profiling).

    • Enabled individualization and discrimination among people based on distinct variation patterns within their DNA.

  • CODIS (Combined DNA Index System):

    • An electronic database system established and maintained by the Federal Bureau of Investigation (FBI).

    • Enables federal, state, and local crime laboratories to exchange, compare, and match DNA profiles across criminal investigations.

  • The Innocence Project:

    • Core Mission: An organization dedicated to exonerating individuals who have been wrongfully convicted of crimes, predominantly through post-conviction DNA testing.

    • Policy Objectives: Works to implement institutional reforms within the criminal justice system to prevent future wrongful convictions.

Structure and Services of United States Crime Laboratories

  • Major Federal Crime Laboratory Organizations:

    • Federal Bureau of Investigation (FBI): Investigates violations of federal laws and operates a comprehensive, full-service federal forensic science laboratory.

    • Drug Enforcement Administration (DEA): Investigates federal controlled-substance crimes and enforces regulatory statutes governing illegal drug distribution and manufacture.

    • Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF): Investigates offenses involving firearms, explosives, acts of arson, and federal alcohol and tobacco regulatory violations.

    • U.S. Postal Inspection Service: Investigates criminal acts involving the United States postal system, postal infrastructure, and the transport of illegal materials via mail.

  • Specialized Crime Lab Units and Operational Scope:

    • Biology Unit:

    • Identifies and analyzes biological evidence, including blood, semen, saliva, hair, and other body tissues.

    • Performs serological testing and generates DNA profiles for identification.

    • Physical Evidence Unit:

    • Examines and compares non-biological physical and trace materials.

    • Analyzes evidence such as paint chips, glass fragments, soil samples, hairs, and textile fibers.

    • Firearms Unit:

    • Examines firearms, discharged ammunition, spent cartridge cases, shot shells, and toolmarks.

    • Conducts comparative assessments to determine if a specific projectile or cartridge case was discharged from a suspect weapon.

    • Ballistics Pioneer: Calvin Goddard pioneered comparative forensic firearms examination methodologies.

    • Document Unit:

    • Examines questioned documents to determine authenticity, detect alterations, and identify authorship.

    • Analyzes handwriting, hand printing, typewriter script, computer printouts, inks, and papers.

    • Individual Characteristics: Specific, unique habits and morphological features associated with a single, identifiable source (such as unique handwriting traits).

    • Exemplars: Known, verified reference samples (e.g., standard handwriting specimens) gathered from a known individual used for direct comparison against questioned evidence.

    • Photography Unit:

    • Employs specialized photographic techniques to document crime scenes, physical evidence, and victim/suspect injuries.

    • Produces detailed visual records for court presentation and forensic archival purposes.

    • Toxicology Unit:

    • Analyzes biological specimens (blood, urine, vitreous humor, organs) to detect the presence and quantify the concentration of drugs, alcohol, poisons, and other toxic chemicals.

    • Fingerprint Unit:

    • Develops, visualizes, records, and compares latent, patent, and plastic friction ridge impressions.

    • Polygraph Unit:

    • Conducts physiological interrogations by measuring and recording autonomic responses, including respiration rate, pulse/blood pressure, and galvanic skin response (skin conductivity).

    • Operational Limitation: A polygraph measures physiological stress responses rather than directly detecting deception; its outputs possess distinct investigative and evidentiary limitations.

    • Voiceprint Analysis Unit:

    • Evaluates and compares recorded verbal communications.

    • Utilizes a sound spectrograph to transform audio speech frequencies into visual graphic displays (voiceprints) for source identification.

    • Forensic Computing:

    • Identifies, collects, extracts, and analyzes digital evidence preserved on desktop computers, mobile phones, external storage media, and cloud networks.

    • Crime Scene Investigation (CSI) Unit:

    • Dispatches trained personnel to crime scenes to document spatial relationships, photograph evidence, conduct systematic physical searches, and recover and package evidence.

    • Ensures strict adherence to proper evidence handling and continuity of possession to safeguard the chain of custody.

Legal Standards for Scientific Evidence

  • Frye v. United States (1923):

    • Frye Standard: Mandated that to be admissible in court, a scientific technique, deduction, or test must be sufficiently established to have gained "general acceptance" within the particular scientific field to which it belongs.

  • Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993):

    • Daubert Standard: The Supreme Court held that the Federal Rules of Evidence superseded the Frye standard in federal jurisdictions, establishing that federal judges must independently determine whether expert scientific testimony is both relevant and reliable.

    • Daubert Evaluation Guidelines/Factors:

    • Whether the scientific technique or theory can be (and has been) empirically tested.

    • Whether the theory or technique has been subjected to peer review and publication.

    • The known or potential rate of error associated with the technique.

    • The existence and maintenance of standardized operational protocols and controls governing the technique's implementation.

    • Whether the technique has attained general acceptance within the relevant scientific community.

  • The Trial Judge as "Gatekeeper":

    • Under the Daubert ruling, the trial judge acts as a gatekeeper tasked with the explicit judicial duty of evaluating whether proposed scientific or expert testimony satisfies statutory criteria for admissibility prior to being heard by a jury.

Classification and Evaluation of Evidence

  • Circumstantial Evidence:

    • Definition: Evidence that implies a fact or supports a legal conclusion indirectly, requiring the finder of fact (judge or jury) to draw a logical inference or presumption connecting the evidence to the proposition.

    • Examples:

    • Latent fingerprints found at a crime scene matching a suspect.

    • Nuclear or mitochondrial DNA recovered from an item handled during an offense.

    • Muddy shoe impressions leading away from an entry point.

    • Possession of property that was recently reported stolen.

    • Evidentiary Function: These facts corroborate hypotheses or demonstrate opportunity, presence, or possession, but do not directly observe or prove the unlawful act itself.

  • Direct Evidence:

    • Definition: Evidence that, assuming it is genuine and believed by the fact-finder, directly establishes a fact or proposition without the requirement of any intervening inference or deduction.

    • Examples:

    • Eyewitness testimony from an individual stating they directly observed the suspect execute the criminal act.

    • An unobstructed, clear video recording documenting the commission of the offense as it unfolds.

    • A voluntary confession admitting to the specific factual elements of a crime.

  • Objective vs. Subjective Evidence:

    • Objective Evidence: Data and physical documentation that exist independent of personal bias, interpretation, or human perception.

    • Subjective Evidence: Evidence that relies upon personal human evaluation, memory, visual perception, or interpretive judgment.

  • Reliability Considerations:

    • Eyewitness testimony is vulnerable to human error and psychological distortion.

    • Scientific evidence possesses intrinsic limitations that depend on protocols for sample collection, contamination control, analytical instrumentation, and expert interpretation.

    • Circumstantial evidence is not inherently weaker or less reliable than direct evidence; both categories require independent contextual evaluation for credibility, precision, and weight.

Witness Testimony in Legal Proceedings

  • Expert Witness:

    • Definition: An individual possessing specialized knowledge, advanced training, formal education, skill, or practical experience beyond that of an average person, qualifying them to evaluate technical data.

    • Evidentiary Authority: Qualified to render professional inferences and express expert opinion testimony within their verified field of expertise, alongside factual recitations.

    • Duties and Ethical Responsibilities:

    • Articulate complex, technical information in terms accessible to the court.

    • Disclose and defend their educational credentials, experience, and methodological standards under examination.

    • Derive conclusions exclusively from sufficient factual data and scientifically reliable methods.

    • Delineate the limits of their analytical findings rather than asserting unwarranted absolute certainty.

    • Maintain impartiality as an objective educator for the court rather than operating as an advocate for either the prosecution or defense.

  • Lay Witness:

    • Definition: An ordinary citizen called to testify whose knowledge of the matter is restricted entirely to firsthand, personal knowledge and observations.

    • Evidentiary Scope: Must testify purely to observable facts, events, and sensory experiences; prohibited from offering specialized, scientific, or technical opinions.

    • Reliability and Factors Affecting Accuracy:

    • Eyewitness testimony is susceptible to degradation and cognitive errors.

    • Human memory and perception can be adversely degraded by elevated stress levels, inadequate lighting, excessive physical distance from the event, brief observation intervals, the passage of time before retrieval, and post-event suggestion or leading questioning.