IAI CCSI: Crime Scene Investigation

Crime Scene Investigation is the IAI CCSI domain that tests whether you can secure, document, search, and process a scene so physical evidence survives courtroom scrutiny. Questions mix field procedure with legal defensibility: contamination control, documentation sequence, packaging choices, chain of custody, and reconstruction reasoning.

Core rules

• First-responder priorities: preserve life, secure the scene, detain witnesses, request resources, and start a scene log. Do not process before security is established.
• Treat every scene as a potential biohazard. Wear nitrile gloves, change them between evidence items, and use masks, eye protection, and shoe covers as needed.
• Establish boundaries and a single entry/exit path to reduce contamination. Record who enters, when, and why.
• Document before you move: notes, overall/mid-range/close-up photographs with scales, then a sketch with measurements. Negative findings such as no forced entry or no blood in a room belong in notes.
• Choose a search pattern by scene shape and evidence type: line/strip, grid, zone, spiral, or ray. Grid suits outdoor areas; zone works for large or cluttered interiors.
• Package each item separately, label and seal it, and record every transfer. Air-dry wet biological evidence; place sharp items in puncture-resistant containers.

Worked example

A forced-entry burglary leaves a broken window, a bloody footwear impression in the hallway, and a dropped glove. The examiner secures the scene, photographs the window before moving glass, swabs the window frame for DNA, casts the impression, and collects the glove in a paper bag. Control swabs from adjacent areas are taken. Each item receives a unique number, seal, and chain-of-custody entry. Reasoning: the window and hallway are separate evidence zones; photographing first preserves context; air-drying and paper packaging prevent degradation; controls strengthen DNA interpretation.

Traps

Moving items before photography; touching surfaces without PPE; packaging wet biological evidence in plastic; chain-of-custody gaps; ignoring transfer and exit routes; treating one room as the whole scene.