IAI CCSI cheat sheet
IAI CCSI · Keep the key ideas within reach.
Crime Scene Investigation
Scene security: establish a perimeter, log every person entering or leaving, and record the scene in its original condition before any alteration; only documented, necessary personnel enter.
Documentation sequence: overall photographs, then mid-range, then close-up with and without scale; photographs precede sketches, and sketches precede collection; the scene log, photo log, and sketch must be mutually consistent.
Chain of custody must be unbroken: each transfer records item description, collector, date, time, location, and recipient; a gap or unexplained break undermines admissibility and evidentiary weight.
Search patterns map to scene type: line/strip for large open areas, grid (double strip) for thorough ground coverage, spiral for confined or circular spaces, zone for vehicles and buildings, and point-to-point for scenes with a known focal area.
Locate evidence in three dimensions using two fixed reference points plus a measurement method: triangulation, baseline offset, polar coordinates from a datum, or a surveyed grid; record the datum and units.
Contamination control: change gloves between items, use disposable tools or clean reusable ones, air-dry wet biological evidence, package each item separately, and never package items together that could transfer trace material.
Biological evidence handling: blood and other fluids are packaged in breathable paper and dried; DNA is degraded by heat, moisture, and sunlight; reference samples from known persons are collected separately and labeled as such.
Latent print development follows a decision tree by surface and porosity: powders and cyanoacrylate for nonporous surfaces, ninhydrin or DFO for porous paper, iodine fuming and silver nitrate for select substrates, and physical developer for wet porous items.
Scene reconstruction uses bloodstain pattern geometry: angle of impact from the width-to-length ratio of an ellipse (sin of angle equals width divided by length), and area of origin from stringing or trigonometric back-projection of at least two stains.