IAI CSCSA cheat sheet

Crime Scene Investigation

• First responder priorities in order: scene safety and medical aid, scene preservation and perimeter control, then notification of investigators; evidence integrity depends on these being done before any collection.

• Scene search patterns map to scene shape: line/strip for large open outdoor areas, grid (double strip) for thorough outdoor coverage, spiral for small or circular scenes, zone/quadrant for large or irregular areas, wheel/ray for small concentrated central scenes.

• Chain of custody requires an unbroken documented record for each item: who collected, date/time, location, description, and every transfer with signatures; gaps create admissibility challenges.

• Locard's exchange principle: every contact leaves a trace; perpetrator-to-victim, perpetrator-to-scene, and victim-to-scene transfers are all bidirectional and worth documenting.

• Biological evidence handling: air-dry before packaging, package in paper (not plastic) to prevent moisture and mold, store cool and dry; wet packaging degrades DNA and promotes putrefaction.

• Rough sketch includes fixed reference points, measurements taken at right angles to two permanent references, north arrow, scale, legend, and item numbers; the final sketch is drawn to scale from these field notes.

• Photography sequence: overall, mid-range, and close-up with and without a scale; a scale is placed in the same plane as the evidence and the photo log records frame, subject, and direction.

• Threshold/point-of-entry documentation: note tool marks, trace evidence, forced-entry damage, and footwear impressions on both sides of the entry; the path taken by the suspect defines the likely evidence trail.

• Deceased-scene roles: coroner/medical examiner establishes cause and manner of death and controls the body; investigators document position, livor, rigor, and scene conditions before removal.