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.