A crime scene is a one-time opportunity: process it badly and evidence is lost or contaminated for good. That's why scene work follows a disciplined sequence rather than an eager rummage.
The stages
- Secure and preserve. The first priority is safety, then establishing a cordon and controlling access so nothing is added, moved or lost. A record is kept of everyone who enters.
- Assess and plan. Before touching anything, investigators survey the scene, identify hazards and fragile evidence, and plan a route and strategy.
- Document. The scene is recorded as found — notes, photographs and sketches — so its original state is preserved even after items are removed.
- Search. A systematic search pattern (grid, spiral or zone) ensures nothing is missed.
- Collect and package. Evidence is recovered with clean, single-use tools, packaged appropriately (paper for biological evidence), and labelled at once.
- Maintain the chain of custody. Every item is logged and its movements recorded from scene to laboratory to court.
Why order matters
Each step protects the next. Documenting before collecting preserves context; searching systematically before disturbing the scene avoids destroying fragile traces; strict access control and clean tools prevent contamination. The most fragile and transient evidence is prioritised.
The people
Scenes involve first officers, scene investigators, a scene manager and specialists — fingerprint officers, forensic scientists, sometimes a pathologist. The common discipline is the same for all: add nothing, lose nothing, and record everything — because the scene can only be worked once.