Untitled Flashcard Set

Crime Scene Investigation & Evidence Collection Notes

What Is a Crime Scene?

• A crime scene is any location where a crime has occurred and evidence may be found.
  
  

• Includes: primary and secondary scenes.
  
  

• Primary Scene: Original location of the crime.
  
  

• Secondary Scene: Any additional location related to the crime (ex. where body/evidence is moved).
  
  

• Goal: Identify, document, and collect evidence without contamination.
  
  

Crime Scene Examples

• Murder in a home → Primary Scene = The home; Secondary Scene = Location where body was transported.
  
  

• Bank robbery → Primary Scene = The bank; Secondary Scene = The motel.
  
  

• Kidnapping → Primary Scene = Mall; Secondary Scene = Cabin.
  
  

Locard’s Exchange Principle

• Developed by Dr. Edmond Locard (“Sherlock Holmes of France”).
  
  

• Phrase: “Every contact leaves a trace.”
  
  

• Applies to trace evidence such as hair, fibers, paint, gunshot residue, soil, etc.
  
  

First Responder Duties

• Secure the Scene: First priority = Safety of individuals present; limit number of people entering.
  
  

• Provide Emergency Aid: Ensure life is protected before evidence collection.
  
  

• Limit/Document Personnel Entry: Keep a log of everyone entering/exiting.
  
  

• Initial Assessment: Quick scan to identify hazards and overall situation.
  
  

• Notify Investigative Team: Call detectives, forensic unit, medical examiner, etc.
  
  

Seven S’s Overview

1. Secure the scene
   
   

2. Separate the witnesses
   
   

3. Scan the scene
   
   

4. See the scene
   
   

5. Sketch the scene
   
   

6. Search for evidence
   
   

7. Secure the collected evidence
   
   

Secure the Scene

• What it means: Establish boundaries with tape/barriers.
  
  

• Why important: Prevents evidence contamination or tampering.
  
  

• What it looks like: Police tape, officers guarding entrances.
  
  

Provide Emergency Medical Aid

• First priority: Save lives.
  
  

• Risk: Medical personnel may disturb/move evidence.
  
  

• Responder must: Document any movement/changes made to aid victims.
  
  

Limit and Document Scene Access

• Maintain a log of: Everyone who enters/exits.
  
  

• Why important: Preserves chain of custody and limits contamination.
  
  

• What it looks like: Sign-in sheet or officer posted at entry.
  
  

Separate the Witnesses

• Why important: Prevents collusion or influence.
  
  

• Sample Questions:
  
  

  • When did the crime occur?
    
    

  • Who called it in?
    
    

  • Who is the victim?
    
    

  • Can the suspect be identified?
    
    

  • What did you see happen?
    
    

  • Where were you when it happened?
    
    

Scan the Scene

• Purpose: Plan documentation strategy.
  
  

• Identify primary scene: Where crime occurred.
  
  

• Identify secondary scene: Related location.
  
  

• Initial assessment: Quick visual scan (not evidence collection).
  
  

See the Scene – Forensic Photography

• Forensic photography documents and preserves the original scene.
  
  

• Used with notes and sketches.
  
  

• Shows: overall layout, evidence, relationship between objects.
  
  

Photography – Rule of Unaltered Scene

• Most important rule: Do not move objects before photographing.
  
  

Photography – Criteria for Admissibility

• Must:
  
  

  • Accurately reflect the scene
    
    

  • Document location and condition of evidence
    
    

  • Be clear and relevant
    
    

Photography – Digital

• Preferred method today.
  
  

• Made using digital cameras; allows immediate review/storage.
  
  

Photography – What to Photograph

• Crime area
  
  

• Adjacent areas
  
  

• Entry/exit points
  
  

• The body (if present)
  
  

• Evidence
  
  

Photography – Overview Photos

• Show the entire scene.
  
  

• Taken from: wide angles, corners of rooms.
  
  

• May include: witness/suspect POV.
  
  

Photographing Evidence

• The item of evidence must be in the photo.
  
  

• Each photographed at multiple angles and distances.
  
  

• Minimum = 4 photos per item (overall, midrange, close-up, close-up with scale).
  
  

Photography – Oblique Lighting

• Used when: Evidence is faint/latent (ex. footprints, fingerprints).
  
  

• Works by: Angling light across the surface.
  
  

• Helps show: Impressions, textures.
  
  

Sketch the Scene

• Purpose: Provide accurate measurements and relationships between evidence.
  
  

• Types: Rough sketch = done at scene; Final sketch = cleaned up for court.
  
  

• Key Elements: Scale, legend, compass direction, case info, measurements.
  
  

Sketch – Measurement Methods

• Baseline (90°) method: Right angles from fixed baseline.
  
  

• Triangulation method: Use two fixed points to measure to evidence.
  
  

Search for Evidence

• Line/Strip Search: Straight lines across scene (outdoors).
  
  

• Grid Search: Double line search (more thorough).
  
  

• Spiral Search: Spiral from center outward or vice versa.
  
  

• Quadrant/Zone Search: Divide into sections.
  
  

• Wheel/Ray Pattern: Outward lines from center.
  
  

Secure the Collected Evidence

• Paper bindle: Holds trace evidence (hair, fibers).
  
  

• Chain of custody: Written record of who collected/handled evidence.
  
  

Collecting Evidence Properly

• Always wear gloves.
  
  

• Use forceps, tweezers, swabs to collect.
  
  

• Handle evidence minimally.
  
  

• Package each item separately.
  
  

Labeling Evidence

• Must include: Case number, item number, description, date/time, collector’s name.
  
  

• Maintain chain of custody by documenting every transfer.
  
  

• Common mistakes: Not sealing properly, mixing items, poor documentation.
  
  

Types of Evidence

• Physical: Weapons, bullets, clothing, glass.
  
  

• Biological: Blood, saliva, hair, DNA.
  
  

• Trace: Fibers, soil, paint chips, gunshot residue.
  
  

• Digital: Emails, texts, GPS data, computer files.
  
  

• Documentary: Contracts, letters, receipts.
  
  

Direct vs Circumstantial Evidence

• Direct evidence: Firsthand observations (eyewitness, video).
  
  

• Circumstantial evidence: Indirect; suggests fact (fingerprints, DNA, motive).
  
  

Chain of Custody – Definition

• Continuous documented record of who collected, handled, and stored evidence.
  
  

• Why it matters: Ensures evidence integrity; admissible in court.
  
  

Chain of Custody – Form

• Includes: Case number, Item number, Description, Collector, Date/Time, Transfers.
  
  

Mini Case Study – The Locker Room Mystery

• Evidence to collect: Clothing, lockers, fingerprints, footprints, hair/fibers, surveillance footage.
  
  

• Maintain chain of custody: Proper packaging, sealed evidence bags, labeling, and detailed transfer documentation.