Section 5.1: Crime Scene Management & Investigations

Crime Scene Management & Investigations

The integrity of any criminal investigation rests entirely on the initial response and management of the crime scene. A peace officer’s primary responsibility upon arrival is to stabilize the scene, preserve physical evidence, and document the environment with meticulous detail. Any compromise at this early stage can jeopardize the prosecution of a case and undermine the justice system. The handling of a scene is a systematic process that balances the immediate need for safety with the long-term requirements of evidence admissibility in a court of law.

1. Initial Response: Safety First

The first responding officer must prioritize human safety over evidence collection. The priority of life hierarchy dictates that the safety of officers, victims, and the public is paramount. The initial response involves several critical steps:

• Neutralizing Threats: Ensuring the scene is safe by securing suspects and checking for active hazards (e.g., armed subjects, hazardous materials, fire).
• Providing First Aid: Officers must render medical assistance to injured parties or coordinate with Emergency Medical Services (EMS). While medical personnel must access the scene, officers should guide them to minimize scene disruption and document any movement of the victim or alteration of clothing/surroundings.
• Securing Suspects and Witnesses: Suspects should be detained immediately. Witnesses must be identified and separated to prevent them from discussing the incident and contaminating each other's recollections.

2. Establishing Scene Boundaries: Perimeters

Once the scene is safe, the officer must establish physical perimeters to control access and protect evidence. Perimeters should be established larger than the suspected scene and later narrowed if necessary, rather than starting small and expanding.

• Inner Perimeter (Hot Zone): This area encompasses the actual scene where the crime occurred and where physical evidence is concentrated. Access is strictly restricted to essential personnel directly involved in processing the scene (e.g., crime scene investigators, investigators). A crime scene entry log must be maintained, recording the name, agency, time of entry, and reason for entry for every individual who enters this zone.
• Outer Perimeter (Cold Zone): This area surrounds the inner perimeter and acts as a buffer. It is used for staging emergency vehicles, setting up a command post, hosting media briefings, and housing support personnel. It prevents the public and unauthorized officers from entering the inner perimeter.

3. Scene Documentation

Documentation provides a permanent, objective record of the scene before any evidence is disturbed. It relies on three primary methods:

• Investigative Notes: Officers must take contemporaneous, chronological, and highly detailed notes. Notes should include arrival times, weather conditions, lighting, smells, transient evidence (e.g., ice melting, footprints in snow), and statements made by individuals on scene.
• Crime Scene Photography: Photos must be taken in a systematic progression:
  1. Overall (Wide-Angle): Captures the entire scene and its surroundings, showing reference points like street signs or house numbers.
  2. Mid-Range (Medium): Establishes the relationship between items of evidence and the overall scene (e.g., showing a firearm relative to a body).
  3. Close-Up: Captures individual items of evidence in detail. Close-ups must be taken first without a scale (ruler) and then with a scale to document the actual size of the item.
• Crime Scene Sketching: A sketch complements photographs by showing precise spatial relationships and dimensions. A rough sketch is drawn at the scene (not to scale but containing accurate measurements) using mapping methods:
  • Rectangular Coordinates: Measuring distance from two perpendicular walls/objects.
  • Triangulation: Measuring distance from two fixed reference points (e.g., a door frame and a radiator) to the evidence, forming a triangle.
  • Baseline Mapping: Establishing a straight line across the scene and measuring perpendicular distance from that line. A final sketch is later prepared using computer-aided design (CAD) software for courtroom presentation.

4. Evidence Preservation & Collection

Evidence must be collected and packaged to prevent damage, contamination, or loss. Key standards include:

• Chain of Custody: The continuous, unbroken record of every individual who has custody of a piece of evidence from the moment of collection until it is presented in court. A meaningful break that suggests tampering or unreliable handling can result in the evidence being ruled inadmissible.
• Contamination Prevention: Officers must wear personal protective equipment (PPE), particularly clean nitrile gloves, which must be changed frequently between handling different items of evidence to prevent cross-contamination or DNA transfer.
• Packaging Standards:
  • Biological/Wet Evidence (e.g., blood-soaked clothing): Must be air-dried and packaged in breathable paper bags or cardboard boxes. Placing wet evidence in plastic bags traps moisture, leading to mold growth that destroys DNA.
  • Dry/Trace Evidence (e.g., hair, fibers, glass): Should be packaged in a paper fold (druggist fold) and placed in a sealed envelope.
  • Firearms: Must be rendered safe (unloaded) before packaging. The cylinder, slide, or chamber should be secured, and details of the firearm's condition (e.g., rounds in chamber, safety position) must be documented.
  • Arson/Accelerant Evidence: Must be sealed in airtight clean paint cans or glass jars to prevent volatile compounds from evaporating.

5. Evidence Search Patterns

When processing a crime scene, investigators utilize structured search patterns to ensure no evidence is overlooked. The choice of pattern depends on the size and nature of the scene:

• Strip or Lane Search: Used for large, outdoor areas. Officers walk in parallel lines (lanes) from one boundary to the other, searching the ground in front of them.
• Grid Search: A more thorough variation of the strip search. After completing a strip search in one direction, officers repeat the search in a perpendicular direction, creating a grid pattern.
• Spiral Search: Conducted by walking in a circular path. The search can start at the center and spiral outward (inward-outward) or start at the perimeter and spiral inward (outward-inward). This is typically used in scenes with no physical barriers.
• Quadrant or Zone Search: The scene is divided into sectors or zones (e.g., rooms of a house), and each zone is assigned to a specific officer or team to search thoroughly.