Crime Scene Investigation: Procedures, Evidence Handling, and Documentation

Purpose of a preliminary walk-through

To get an overall view of the crime scene and note evidence or conditions that could change over time.

Who performs the preliminary walk-through?

The first officer on the scene, the crime scene investigator, and sometimes the lead detective.

Medical examiner's job if there is a death

To examine the body, note its condition, and estimate the time of death.

Type of lighting that reveals hidden evidence

Oblique lighting — a flashlight is shined at a low angle to spot details not seen under normal light.

How should notes of the crime scene be taken?

Completely, clearly, and in order — describing every action, observation, and piece of evidence.

Importance of photographs

They capture details that may be missed and show the scene exactly as it was found.

When should crime scene photos be taken?

Before anything is touched, moved, or examined.

Importance of using a ruler in photos

To show the actual size and scale of the evidence.

How should videotaping be done?

Start outdoors, move indoors while narrating, and keep the video unedited as evidence.

Importance of sketches in addition to photographs

They show measurements, scale, and placement of objects, giving a clearer layout of the scene.

Line or strip method

Investigators walk side by side in straight lines across a large area to look for evidence.

Grid method

Investigators search in one direction, then again at a right angle to cover the area thoroughly.

When is the zone method used?

In buildings or houses, dividing areas into smaller sections for teams to search.

When is the wheel or spiral method used?

In small, open areas — starting at the center and moving outward in a circular pattern.

Why should each piece of evidence be packaged separately?

To prevent contamination or evidence from mixing or transferring materials.

What type of evidence is packaged first?

The most fragile evidence, like fingerprints, blood, or trace materials.

How are wet items packaged?

They are dried first, then packaged to prevent mold and mildew.

How are firearms packaged?

They are unloaded and secured in a rigid wooden container to prevent movement.

What is the chain of custody?

A written record of everyone who handled the evidence and when, from collection to court.

JonBenét Ramsey Case — 3 ways the crime scene was not properly handled

Too many people entered the house, contaminating the scene. Evidence was moved and touched before being documented. The body was moved from its original location, destroying key evidence.

Importance of sketches and photographs in a crime scene

Both are essential for documentation — Photographs capture details and preserve a visual record of how the scene looked. Sketches show accurate measurements, scale, and relationships between objects.