Crime Scene Investigation Overview

Throwing a Ball

  • To throw a ball that returns to you, throw it straight up.

Crime Scene Investigation: Introduction

  • Importance of observations at a crime scene.

  • Need for accuracy in recording and reporting observations.

Observation Issues

  • Perception can be limited and incorrect.

  • Filters in the brain affect what details are noticed.

  • Previous knowledge can skew perception of new situations.

Witness Account Reliability

  • Eyewitness accounts can differ due to perception filters.

  • Stressful situations can heighten observation abilities.

  • Innocence Project shows 87% of wrongful convictions due to faulty eyewitness accounts.

Processing the Crime Scene

  • Goal: Recognize, document, and collect evidence.

  • Based on Locard's Principle: "Every contact leaves a trace."

Types of Evidence

  • Direct Evidence: Proves/disproves fact without assumptions (e.g. eyewitness accounts, videos).

  • Circumstantial Evidence: Indirect, implies facts without direct proof (e.g. fingerprints, DNA).

Significance of Evidence

  • Identification: Determines physical/chemical identity of substances.

  • Comparison: Compares samples to determine if they are from the same source, factoring in probability.

Evidence Characteristics

  • Individual Characteristics: Unique to a source (e.g. matching fingerprints).

  • Class Characteristics: Common to a group (e.g. blood type).

7 S's of Crime Scene Investigation

  1. Secure the Scene: Ensure safety and prevent unauthorized access.

  2. Separate Witnesses: Prevent collaboration; compare accounts later.

  3. Scanning the Scene: Identify primary/secondary crime scenes.

  4. Seeing the Scene: Photograph and document scene accurately.

  5. Searching for Evidence: Use systematic patterns for thorough evidence search.

  6. Securing Evidence: Properly package and label evidence.

  7. Scene Reconstruction: Analyze evidence to reconstruct the crime events logically.