"The 7 S's of Crime Scene Investigation''

From a forensic standpoint, crime scene investigation (CSI) is the systematic and scientific process of investigating a crime scene in order to find, gather, store, and examine tangible evidence that can be used to recreate events, identify suspects or victims, and assist with legal processes.

Blog Jun 25, 2025 0 64 Add to Reading List

"The 7 S's of Crime Scene Investigation''

The seven crucial stages that crime scene investigators must take to guarantee a systematic and legally sound approach to processing a crime scene are known as the "7 S's of a Crime Scene." By taking these actions, the scene and the gathered evidence are kept intact.

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Step	Purpose
1. Secure	Protect scene and people
2. Separate	Avoid tainted witness accounts
3. Scan	Identify key areas
4. See (Photograph)	Create a visual record
5. Sketch	Provide a scaled layout of the scene
6. Search	Locate all relevant evidence
7. Secure & Collect	Ensure proper handling and legal admissibility of evidence

1. Secure the Scene

Protecting people and avoiding contamination should come first.The first responding police restricts access and barricades off the area.To record who enters and leaves the scene, a log is started.

2. Separate the Witnesses

Keeping witnesses separate prevents them from conspiring or influencing one another's testimony. In order to obtain objective testimonies, interviews are done independently.

3. Scan the Scene

An initial survey is conducted by the team to ascertain: The central scene, or the location of the crime Any supporting scenes, such as the victim's house or escape routes facilitates the planning of what to record or gather and where to do so.

3. See (Photograph) the Scene

Before anything is moved or touched, pictures and videos are taken. Every angle is recorded: broad perspectives of the entire scene Contextualised medium-range images of the evidence Close-ups of specific pieces of evidence

5. Sketch the Scene

A rough sketch is made of the scene, showing the location of evidence.
Accurate measurements
Scale and direction (usually a north arrow)

Labels for each item of interest

6. Search for Evidence

In forensic science, the process of looking for physical evidence at a crime scene is a rigorous and systematic way to find and retrieve evidence that can be used to reconstruct the incident, identify victims or suspects, and assist with legal investigations.

Types of Physical Evidence Searched

Biological evidence: blood, hair, saliva, semen, tissue
Trace evidence: fibers, glass, paint chips, soil, gunshot residue
Latent prints: fingerprints, palm prints, shoe prints
Weapons: firearms, knives, blunt objects
Digital evidence: mobile phones, laptops, USB drives
Documents or personal belongings

7. Secure and Collect Evidence

Each piece of proof is: gathered with the right instruments in the appropriate containers With comprehensive information labelled In the chain of custody log The admissibility of evidence in court is guaranteed by proper collecting.

Types of Forensic Evidence & Collection Methods

Type of Evidence	Examples	Collection Method	Container Type
Biological	Blood, saliva, semen, hair, tissues	Swabs, forceps, scalpels	Paper envelopes, breathable bags
Trace	Fibers, glass, soil, paint chips	Tweezers, tape lifts	Folded paper (druggist fold), envelopes
Fingerprints	Latent prints	Fingerprint powder and brush, tape lifts, cyanoacrylate fuming	Cards or protective covers
Firearms & Ammo	Guns, bullets, casings	Handle minimally, document serial numbers	Gun boxes with zip ties
Documents	Handwritten notes, printed materials	Do not fold or mark	Document protectors, folders
Digital Devices	Phones, computers, USB drives	Anti-static bags, Faraday bags	Shockproof, anti-static containers
Drugs/Substances	Pills, powders, plant material	Scoop into clean containers, avoid direct contact	Plastic or glass vials, bags
Footwear/Tire Impressions	Impressions in soil or snow	Casting (e.g., with dental stone), photography	Cardboard boxes or casts stored safely