128 Resource book on the use of force and firearms in law enforcement Chapter 8.  Criminal investigation Depending on the circumstances, some use of force may be warranted during a criminal investigation, e.g. to protect evidence from destruction or to restrain an individual who opposes a house search. At the same time, force can also be abused during an investigation, for example when questioning a suspect. This chapter examines the use of force during criminal investigation, looking more closely at criminal investigation methods, the suspect interview and measures that can be taken to prevent the abuse of force in such situations. 8.1. Introduction Law enforcement officials can start a criminal investigation when there are reasonable grounds to believe that a criminal offence has been committed. This must be based on credible information that a crime has or is suspected of having been committed, for example because the law enforcement officials actually witnessed it, a victim reported to the police station, because of found stolen goods, or a dead body that has been discovered. The prime aim of the investigation is to establish the truth and bring the alleged offender, if any, to justice. Regardless of whether or not the identity of the suspect is known at the early stage of the investigation, the aim is to identify and verify the perpetrator. 8.2.  Criminal investigation methods For establishing the facts, law enforcement officials have various information collection methods, including but not limited to: • Crime scene investigation • Body search • House search • Witness interview • Forensics, including taking of fingerprints and medical examinations to detect blood, semen, hair and other forensic materials