Chapter 2: The Crime Scene & Evidence Handling

Initial responsibilities fall to the first officer arriving, who must prioritize rendering aid to victims and apprehending any perpetrators, followed immediately by securing and isolating the area, establishing clear boundaries, and strictly logging every individual who enters or exits the scene. To permanently document the scene in its original state, three recording methods are utilized: meticulously detailed notes that track personnel movements and initial observations; photography, which requires the scene to be unaltered, encompassing overview, medium-range, and close-up views (the latter often utilizing a scale); and sketching, starting with an on-site rough sketch containing accurate measurements from fixed points, which is later converted into a precise, aesthetic finished sketch, frequently using computer-aided drafting (CAD) software. A systematic search for physical evidence must be executed using established patterns like the grid, strip/line, spiral, or quadrant/zone method, chosen according to the area's characteristics. All physical evidence collected must be packaged separately to prevent contact and cross-contamination, with special precautions taken for biological materials, which should be air-dried and stored in porous containers like paper bags to inhibit mold growth, and arson evidence, which requires airtight containers. Throughout the evidence transfer process, the chain of custody must be strictly maintained, documenting every person who has possession of an item to uphold its authenticity in court. Furthermore, investigators must gather standard/reference samples (known materials, such as buccal swabs, for comparison) and substrate controls (uncontaminated materials adjacent to the evidence). Adherence to health and safety standards is paramount, requiring investigators to wear protective gear—including disposable gloves, masks, and shoe covers—to avoid exposure to biological hazards like AIDS or hepatitis B, and prevent contamination of DNA evidence. Finally, all evidence recovery must comply with Fourth Amendment guidelines, as highlighted by Supreme Court decisions like Mincey v. Arizona and Michigan v. Tyler, which severely restrict conducting warrantless searches at crime scenes beyond initial emergency circumstances.