Review slides SRU Spring 2025 (1)

History of Forensic Science

  • Edmond Locard

    • Incorporated Gross' principles into a practical crime laboratory framework.

    • Locard's Exchange Principle: States that when a criminal interacts with an object or person, evidence is transferred in both directions, leading to cross-transfer of evidence.

Definition of Forensic Science

  • Forensic science broadly defined as the application of scientific principles to criminal and civil laws.

  • Focuses on the application of science in the context of criminal justice enforced by police agencies.

Significant Historical Figures

  • Mathieu Orfila: Known as the father of forensic toxicology.

  • Alphonse Bertillion: Developed the first scientific personal identification system in 1879.

Technical Support Services by Crime Laboratories

  • Crime labs provide five basic services:

    • Firearms Unit: Analyzes discharged bullets, cartridge cases, shotgun shells, and ammunition.

    • Document Unit: Conducts handwriting analysis and addresses questioned document issues.

    • Photographic Unit: Uses specialized photography techniques to document physical evidence.

    • Some labs may also provide optional services.

Manner of Death

  • Classified in death certificates as:

    • Homicide

    • Suicide

    • Accidental

    • Natural

    • Undetermined

Types of Evidence

  • Class Characteristics: Evidence associated only with a group, significant for comparisons in criminal investigations due to high diversity in the environment.

  • Individual Characteristics: Unique evidence linked to a single source with a high degree of probability.

Packaging and Contamination

  • Key concern for DNA specimens (e.g., blood, saliva) is contamination.

  • Different items must be placed in separate containers to avoid cross-contamination and damage.

Crime Scene Terminology

  • Primary Crime Scene: Location of the initial crime (e.g., a murder site).

  • Secondary Crime Scene: Location where subsequent events took place (e.g., burial site of a victim).

Technical Support: Optional Services

  • Toxicology Unit: Tests body fluids and organs for drugs/poisons.

  • Latent Fingerprint Unit: Processes evidence for fingerprints.

  • Polygraph Unit: Conducts lie detector tests.

Skills of a Forensic Scientist

  • Forensic scientists must adeptly apply scientific principles and techniques to analyze various evidence types collected during investigations.

Defining a Crime Scene

  • Crime scenes can be classified by:

    • Type of crime (e.g., homicide, burglary)

    • Organization or disorganization of the scene

    • Physical location (indoor, outdoor, vehicle)

    • Criminal behavior associated (passive or active)

Duties of First Responders

  • Upon arrival, first responders must:

    • Provide medical assistance to victims and ensure they do not disturb evidence.

    • Secure the crime scene to prevent unauthorized access.

Recording Methods of Crime Scene

  • Crime scene documentation methods include:

    • Photography: Captures layout and evidence.

    • Sketches: Illustrate spatial relationships of evidence.

    • Notes: Record details that may not be visually captured, though financial or personnel limitations may affect the use of all methods.

Crime Scene Photography

  • Photographs should depict:

    • Overall scene layout.

    • Position of evidence.

    • Perspectives of victims, suspects, and witnesses.

    • Original conditions of evidence items.

Sketching and Physical Evidence

  • Crime scene sketches and photography clarify spatial relationships of evidence.

  • Physical Evidence: Objects establishing whether a crime occurred and linking crime, victim, and perpetrator.

  • Purpose of recognizing physical evidence for collection and analysis, as its judicial weight will ultimately be determined by a jury.

Chain of Custody

  • Maintaining a documented chain of custody is crucial; all individuals handling or examining evidence must be accounted for.

Reference Samples

  • Standard/Reference Sample: Known origin evidence for comparison, crucial for analyzing items like blood or hair samples.

Evidence Collection from Autopsy

  • Items to collect include:

    • Victim’s clothing, fingernail scrapings, hair combings, buccal swabs.

    • Swabs from sexual assault-related areas.

    • Gunshot residue swabs from shooting victims.

Crime Scene Reconstruction

  • Method for estimating event sequences via physical evidence and witness statements.

Use of Physical Evidence in Investigations

  • Key goals include recognizing, collecting, interpreting, and reconstructing relevant evidence.

Types of Information from Evidence Examination

  • Identification of unknown substances, reconstruction of crime events, and providing investigative leads.

Four Steps in Crime Scene Investigation

  1. Recognition: Surveying, documenting, and collecting evidence.

  2. Identification: Comparison testing of collected evidence.

  3. Individualization: Evaluating and interpreting evidence.

  4. Reconstruction: Reporting findings and presenting evidence.

First Responder Responsibilities

  • Duties include assisting victims, capturing and securing the scene, and ensuring communication about scene details to investigators.

Securing the Crime Scene

  • Following Locard’s principle, consistent scene security is important to link evidence to suspects, victims, or witnesses.

    • Different security levels based on importance:

      • Level 1: General public restricted.

      • Level 2: Restricted for official purposes.

      • Level 3: Highest security for key evidence areas.

Crime Scene Survey Process

  • Investigators must survey the scene, noting conditions, weather, entry/exit points, and conducting an initial observation to set further investigation focus.

Effective Crime Scene Note Taking

  • Essential notes should cover:

    • Date and time of notifications.

    • Arrival details and scene descriptions.

    • Victim and team member observations.

Crime Scene Sketching Techniques

  • Two types of sketches: Rough Sketch and Finished Sketch.

  • Views can include Overhead (bird's eye) or Elevation (side view).

Collection and Preservation of Evidence

  • Evidence collection should prioritize fragile items, use appropriate containers, and label each item clearly.

Information from Physical Evidence Examination

  • Evidence links people, scenes, and objects highlighting Locard’s principle: objects in contact will exchange material.

    • Critical for establishing connections in investigations.

Establishing Witness Credibility through Evidence

  • Physical evidence plays a key role in validating witness accounts, especially in cases involving patterned evidence like fingerprints or bloodstains.

Forensic Science in the Laboratory

  • Forensic laboratories handle:

    • Evidence analysis and all related tasks such as recognition, collection, and preservation.

    • Education for law enforcement and judicial personnel on evidence collection and testing principles.