Crime Scene Investigation and Management
The Crime Scene domain tests the whole arc from first response to scene release: scene integrity, documentation, evidence handling, and defensible reconstruction. Questions favour practical decisions under pressure rather than definitions.
First response and integrity
- Render aid, secure and define the scene, then preserve: entry/exit log, PPE, a single cleared path, no food or smoking, no unrecorded movement of items.
- Note the condition of doors, lights and windows on arrival; these are perishable observations.
- Locard's exchange principle underpins why control and reference samples are collected.
Documentation and search
- Notes, then photography (overall → mid-range → close-up with scale), then sketch with measurements from a fixed datum or by triangulation; the sketch records measurements, not artistic impression.
- Search patterns: line/strip, grid, zone, spiral, wheel and link; choose by terrain, scene size and officer numbers.
Evidence handling
- Air-dry biological items and package in breathable paper; rigid containers for sharps and glass; sealed liquid containers; digital devices shielded from network access.
- Chain of custody must be continuous, with each transfer recording date, time, name, and purpose.
Worked example. Blood is found on shards of a broken entry window at a burglary. Note which face of the glass carries the blood and the direction of the fracture radiating lines, because they indicate which side force was applied from. Photograph the shards in place with a scale, then package each shard separately in rigid, labelled containers so edges are not abraded in transit; record the position of each shard before removal.
Traps that cost marks
- Sealing damp bloodstained clothing in plastic, promoting degradation and mould.
- Moving or opening items before the overall photograph is taken.
- Sketching from memory after the scene is released.
- Failing to document the absence of expected evidence.
- Treating a fire or explosion scene like a routine indoor scene without a safety and origin assessment.