Investigative Procedures and Evidence Handling
This domain tests scene management, identification procedures, interview rules, and the chain of custody that keeps physical evidence admissible.
Scene and evidence
- First responder duties: render aid, secure and define the scene, broadcast, start a scene log, avoid contaminating, canvass for witnesses and for cameras.
- Chain of custody must show every transfer: who collected, when, where, packaging, seal numbers, storage, and who accessed it. Any break creates an admissibility argument.
- Biological evidence is air-dried before packaging; wet evidence in plastic degrades. Firearms are unloaded and secured, then swabbed before handling where DNA is at issue.
- Photograph the item in place before moving it, and describe its condition in your notes.
Identification
- A showup is permissible when justified by exigency and conducted near in time and place; it becomes unduly suggestive if you signal the answer.
- Photo arrays should be administered blind or blinded, sequentially, with a standard instruction that the administrator does not know the suspect. Preserve the array and all notes.
- Suppression turns on suggestiveness plus reliability under the Manson v. Brathwaite factors.
Interviews and disclosure
- Miranda requires custody plus interrogation; the public safety exception is narrow and temporary.
- New York's right to counsel is indelible once it attaches, and questioning on an unrelated matter while the person is represented can be barred.
- CPL § 245.20 discovery covers all notes, recordings and reports; Rosario and Brady duties are continuing.
Worked example
You recover a handgun from a stairwell. Photograph it in place, note the exact step and orientation, swab for DNA before handling, unload and voucher it with a seal number, then request a lab examination. If the voucher number on the property receipt does not match the envelope, expect a challenge.
Traps
Bagging wet evidence in plastic; letting one officer collect and store everything without documentation; failing to preserve the photo array; treating memo book entries as personal notes rather than discoverable material.