Scene Examination, Documentation, and Evidence Handling
Scene examination and documentation
Secure and control the scene first: establish a perimeter, an entry log, and a safety assessment covering structural stability, electrical hazards, HAZMAT, and atmosphere. Document before you disturb. Photograph systematically - overall, mid-range, close-up with scale - and keep a photo log. Prepare measured sketches and contemporaneous notes. Video walkthroughs and 3D scans supplement but do not replace still images and written records.
Evidence handling
Collect, package, and preserve. Ignitable liquid residue samples go into clean, unused metal cans or approved airtight containers; never plastic, because vapors permeate and distort results. Biological or DNA evidence goes into breathable paper packaging; sharp items get protective covers. Maintain chain of custody with each transfer logged (who, what, when, why). Document sample location, depth, and substrate - char, soil, concrete. Collect control or comparison samples from an unaffected area so the laboratory has a baseline. Take representative samples and no more than necessary.
TRAP: A plastic bag used for an ignitable-liquid sample, a gap in the chain-of-custody log, or a photograph taken after the scene was altered.
RULE OF THUMB: Metal for volatiles, paper for biological, sealed and labeled for everything - if the container can outgas or leak, it is the wrong container.