Criminal Investigation and Detection
What this domain tests
Criminal Investigation and Detection tests the systematic process of identifying, locating, collecting, preserving, and presenting evidence to establish a crime and identify the offender.
Core rules
- The investigation process: identify the crime, locate witnesses and evidence, collect and preserve evidence, evaluate, and build the case. The case folder must be complete and chronological.
- Interviews gather information from witnesses; interrogation questions suspects. Both must respect voluntariness and the Bill of Rights.
- Custodial investigation requires Miranda warnings and counsel under RA 7438. A confession without counsel is inadmissible.
- Crime-scene management: secure the scene, document, search systematically, collect and package evidence, maintain chain of custody, and canvass witnesses.
- Entrapment uses an opportunity to catch a willing offender; instigation induces an innocent person to commit a crime. Entrapment is valid; instigation is not.
- In drug buy-busts, the poseur buyer, pre-operation report, marking, inventory, and witnesses are critical.
Worked example
A poseur buyer hands marked money to a seller who delivers a sachet of shabu. Back-up officers arrest the seller. The sachet is marked at the scene, photographed, inventoried with the required witnesses, and submitted for lab examination. The seller claims instigation. Reasoning: the operation is entrapment if the seller was already willing and the officers merely provided the opportunity. If officers induced a previously innocent person, it is instigation and the case fails. The chain of custody must connect the seized sachet to the lab specimen.
Traps
Do not confuse admission with confession. Do not rely on an uncounseled confession. Do not skip the inventory witnesses without explaining why. Do not treat a suspect's silence as guilt. Watch for leading questions, suggestibility, and contamination of the crime scene.