Crime Scene Investigation
Crime Scene Investigation
This domain tests the sequence of scene work - secure, survey, document, collect, package, transfer - and the reasoning behind each step. Questions often present a decision point: what to do first, what to photograph before moving, or how to package a wet item.
First responder duties
Priority is life safety, then scene security: establish a perimeter, keep an entry log, and prevent contamination with PPE and a controlled path. Nothing is moved until the scene is photographed and measured. The scene survey identifies boundaries, hazards, and a search pattern - line/strip, grid, spiral, zone, or wheel - chosen to fit terrain and evidence type.
Documentation
Notes, photography, and sketches are complementary, not redundant. The sketch records measurements from fixed reference points, not from the body or from evidence, and includes a legend and north arrow; it is drawn to scale or clearly marked not to scale. Photographs proceed from overall to midrange to close-up, with and without a scale.
Worked example
A bloodstained shirt is found damp in a bathroom. Correct handling: photograph in place with a scale, then air-dry in a secure, clean space away from sunlight and traffic; package in paper, not plastic, because trapped moisture promotes mold and degradation; label with item number, collector, date, and location; record every transfer on the chain-of-custody form. Plastic becomes acceptable only after thorough drying, and even then paper is preferred.
Traps
Collecting before photographing; sketching measurements taken from the body; sealing wet evidence in plastic; failing to log a custody transfer; using the same gloves across items; and treating a seemingly clean scene as needing no documentation.