Scientific Method in Forensic Science Flashcards

Foundations of Scientific Thinking in Forensic Science

• Course Context: Course FORS2216 taught by Dr. Fikiet.

• Science vs. Pop Culture: The widespread popularity of forensic science in media and pop culture often obscures the underlying rigorous scientific principles. The discipline is formally designated as forensic science because it relies directly upon the application of the scientific method.

• Cognitive Frameworks (System 1 vs. System 2 Thinking):

  • Cognitive processing is divided into two operational modes: System 1 (fast thinking) and System 2 (slow thinking).

  • System 1 (Fast Thinking): Automatic, intuitive, and rapid decision-making mechanism. While much of human thought naturally occurs in this mode, it is susceptible to cognitive biases and quick assumptions.

  • System 2 (Slow Thinking): Deliberate, analytical, logical, and methodical reasoning process required for scientific investigation.

  • Transitioning Systems: Forensic scientists must recognize when to deliberately disengage System 1 and switch to System 2 thinking.

  • Domain Knowledge: Effective execution of System 2 thinking requires a substantial foundation of specific information, termed domain knowledge. Domain knowledge forms the essential foundation for analyzing evidence, formulating hypotheses, and drawing scientific conclusions.

  • Reference resource: https://www.youtube.com/watch?v=JiTz

The Scientific Method Framework

• Sequential Process Flow:

  1. Question: Identification of a specific, defined inquiry regarding evidence or scene dynamics.

  2. Hypothesis: Formulation of a testable and falsifiable proposed explanation based on domain knowledge.

  3. Experimentation: Implementation of controlled analytical testing procedures to test the hypothesis.

  4. Results: Acquisition and compilation of empirical analytical data.

  5. Evaluation: Assessment of results to determine outcome:

  • If Hypothesis True: Hypothesis is supported by the data.

  • If Hypothesis False: Hypothesis is rejected, necessitating hypothesis refinement or reformulation and subsequent re-testing.

Questions and Hypothesis Development in Forensics

• Investigative Questions: Forensic inquiries must be structured into precise, testable questions derived from crime scene evidence.

  • Shoe Impression Scenario:

  • Investigative Question: "Did this shoe make this print found at the scene?"

  • Comparative analysis evaluates class characteristics (sole pattern, size, brand design) and individual characteristics (wear patterns, cuts, unique marks).

  • Chemical/Powder Scenario:

  • Investigative Question: "What is this substance found at the scene?"

  • Chemical identification requires systematic qualitative and quantitative testing to determine identity and composition.

Experimental Design and Logical Validation

• Experimental Focus: Determining precise variables and parameters requiring testing (e.g., evaluating shoe tread geometry versus illicit powder chemical structure).

• The Wason Selection Task: A logical reasoning puzzle demonstrating the importance of hypothesis falsification over confirmation bias.

• Abstract Rule Scenario:

  • Hypothesis: "If the card shows an even number on one face, then its opposite face is blue."

  • Visible Card Options: 3 (white background), 8 (white background), Blue (blue background), Red (red background).

  • Analytical Objective: Determine which specific cards must be flipped to test the validity of the hypothesis without unnecessary steps.

• Concrete / Social Rule Scenario:

  • Hypothesis: "If you are drinking alcohol, then you must be over 18."

  • Visible Card Options: 16 (age card), 25 (age card), SODA (beverage card), BEER (alcoholic beverage card).

  • Analytical Objective: Select the cards representing the drink status of an underage person (16) and the age of a person consuming alcohol (BEER) to verify compliance or violation of the rule.

Objectives of Applying the Scientific Method

• Accuracy and Precision:

  • Accuracy: Proximity of measurement results to the true value ("ground truth").

  • Precision: Reproducibility and consistency of analytical measurements when repeated under identical conditions.

• Ground Truth: Obtaining conclusions that reflect exact physical reality.

• Bias Minimization: Systematically reducing cognitive, contextual, and analytical bias to achieve objective consistency across examiners.

• Standardization: Utilizing the scientific method to construct formal Standard Operating Procedures (SOPs), testing protocols, and forensic standards.

Laboratory Protocols and Standard Operating Procedures

• Definition of Protocols: Performing exact, reproducible steps for every analysis to eliminate arbitrary changes driven by personal preference or impulse.

• Modifications: Protocol modifications must be grounded in legitimate, scientifically validated justifications.

• Institutional Variability: Individual forensic laboratories establish specialized internal protocols suited to their instrumentation and scope.

  • Proprietary Protocols: Protected internal documentation restricted to agency personnel.

  • Publicly Available Protocols: Standardized guidelines published for open access (e.g., Virginia Department of Forensic Science manuals available at https://dfs.virginia.gov/documentation-publications/manuals/).

• Foundational Standards: Laboratory protocols are derived from published national and international standardization frameworks, including OSAC and ASTM.

Scientific Working Groups (SWG)

• Historical Context: Scientific Working Groups served as the primary precursors to modern forensic standardization bodies.

• Scale & Scope: Organizational sizes varied across different disciplines.

• Key Working Groups:

  • SWGDAM: Scientific Working Group on DNA Analysis Methods.

  • SWGDRUG: Scientific Working Group for the Analysis of Seized Drugs.

  • SWGDRUG monographs remain active, accessible, and continuously updated for illicit drug analysis.

Organization of Scientific Area Committees (OSAC)

• Governance Structure: Established under the NIST (National Institute of Standards and Technology).

• Scope of Coverage: Coordinates standardization across 19 distinct forensic science disciplines.

• Core Focus Areas: In addition to specific discipline subcommittees, OSAC manages research initiatives, measurement science, statistical applications, and Quality Assurance (QA).

• Central Governing Structure:

  • Forensic Science Standards Board (FSSB)

  • Standards Review Panel

  • Emerging Technologies Committees

• Organizational Divisions and Subcommittees:

  • Digital/Multimedia:

  • Digital Evidence

  • Facial & Iris Identification

  • Video/Imaging Technology & Analysis

  • Biology:

  • Wildlife Forensic Biology

  • Human Forensic Biology

  • Seized Drugs & Toxicology:

  • Seized Drugs

  • Forensic Toxicology

  • Trace Evidence:

  • Trace Materials

  • Ignitable Liquids, Explosives, & Gunshot Residue

  • Pattern/Impression:

  • Forensic Document Examination

  • Firearms & Toolmarks

  • Friction Ridge

  • Footwear & Tire

  • Scene:

  • Crime Scene Investigation & Reconstruction

  • Bloodstain Pattern Analysis

  • Dogs & Sensors

  • Medicine:

  • Forensic Anthropology

  • Medicolegal Death Investigation

  • Forensic Nursing

ASTM International Standards

• Organization: ASTM International (formerly American Society for Testing and Materials) provides global consensus standards across industrial and scientific disciplines.

• Active Forensic Standard Examples:

  • ASTM E2937-26:

  • Title: Standard Guide for Using Infrared Spectroscopy in Forensic Paint Examinations

  • Status: Active Standard

  • Last Updated: Aug 03, 2026

  • ASTM E2123-20:

  • Title: Standard Practice for Preservation of Evidence in Sexual Violence Investigation

  • Status: Active Standard

  • Last Updated: Jul 08, 2026