Forensics Unit One: Eyewitnesses and Crime Scenes

Witness Memory

Factors that affect witness memory and confidence include time delay before questioning, number of times questioned, and method of questioning.

Pre-Interview Techniques

Obtain witness statements as close to the event as possible and recreate the scene in their mind before questioning.

Interview Process

Start with unprompted recollection, allow the witness to narrate their story, and record both questions and answers.

Avoiding Bias

Avoid leading questions, asking questions too quickly, and interrupting the witness during the interview.

Suspect Lineups

Foils should resemble the suspect's description, and similar quality should be maintained for pictures of foils and the suspect.

Crime Scene Classification

Primary crime scene is where the crime occurred; secondary crime scene is where an accessory event took place.

Police Role

Isolate the crime scene, detain witnesses, and ensure no one enters or leaves the scene.

JonBenet Ramsey Case

The case involved a ransom note and the discovery of JonBenet's body in the basement of her home.

Crime Scene Documentation

CSI must document evidence through sketches and photographs, ensuring not to touch the scene.

Types of Photographs

Long range shows overall scene, medium range shows evidence proximity, and close-up shows evidence details with measurement devices.

Crime Scene Sketching

Sketches depict layout and relationships of items; rough sketches are basic, elevation sketches show trajectories, and perspective sketches are 3D.

Crime Scene Reconstruction

Supports a likely sequence of events based on evidence and witness statements, requiring objectivity and falsifiability.

Limits of Reconstruction

Avoid fallacy of bifurcation, generalizations, and false linkage when reconstructing events.

Search Patterns

Evidence is searched for on various surfaces and marked with numbers for documentation.

Evidence Collection

Avoid contamination, use appropriate techniques for different types of evidence, and store biological evidence in paper bags.

Evidence Classification

Individual characteristics are unique and linkable, while class characteristics are associated with groups.

Legal Search and Seizure

Maintain a chain of custody for evidence and follow legal protocols for search and seizure.

Presenting Evidence

Frye Standard requires widely accepted methods, while Daubert Ruling allows judges to act as gatekeepers for evidence.

Evidence Classifications

Evidence Classifications

1. Physical Evidence: Tangible items that can be collected and analyzed (e.g., fingerprints, weapons).

2. Biological Evidence: Organic material that can provide DNA (e.g., blood, hair).

3. Digital Evidence: Data stored electronically (e.g., emails, files).

4. Trace Evidence: Small quantities of material transferred during a crime (e.g., fibers, soil).

5. Testimonial Evidence: Statements made by witnesses or experts.

6. Documentary Evidence: Written or recorded materials (e.g., contracts, photographs).