Criminal Investigation
What the exam tests
This domain tests crime-scene preservation, interviews, evidence collection, chain of custody, search warrants, and probable cause. Expect questions on what to do first, how to document, and when a warrant is required.
Core rules
- Secure and control the scene first; identify witnesses, preserve transient evidence, and start a scene log.
- Chain of custody must be continuous and documented from collection to disposition.
- A search warrant affidavit must state facts, not conclusions, and establish probable cause and particularity.
- Interviews should be separate, open-ended first, and documented in the subject's own words.
- Evidence can be seized under plain view only when the officer is lawfully present and the incriminating character is immediately apparent.
Worked example
A burglary victim reports a missing laptop. An officer secures the broken door, photographs it, and interviews the neighbor who saw a man carrying a laptop. The officer writes an affidavit describing the neighbor's statement, the time, the direction of travel, and the suspect description, then obtains a warrant to search the suspect's apartment. Reasoning: the affidavit supplies facts connecting the suspect and item; a warrant is needed before entering the apartment.
Traps
- Entering a home without consent, exigency, or a warrant.
- Writing conclusions such as 'the suspect was nervous' without observable facts.
- Breaking the chain of custody by leaving evidence unsecured.
- Interviewing witnesses together and letting them influence each other.