The criminal investigation process sets the legal guidelines for bringing law enforcement to a crime scene, collecting evidence and prosecuting offenders. The process is vital for preserving the rule of law and providing justice to victims of crime. Investigations require coordination between police, forensic specialists and legal authorities.
A police investigation starts with a crime report, usually submitted to a police station by an individual who has witnessed or been the victim of a specific incident. The report is used to identify a suspect and begin gathering evidence. Police officers will then interview witnesses and gather forensic evidence from the crime scene. This may include photographing a scene, analysing blood or DNA samples or taking voiceprints. All of this is to help the police identify a suspect and decide whether or not to make an arrest.
As investigations progress, detectives must collaborate with prosecutors to ensure that all case elements meet the burden of proof required for conviction. This includes preparing for preliminary hearings, grand jury sessions and trial. This partnership also helps investigators overcome challenges like reluctant witnesses and insufficient forensic results.
A well-rounded investigation requires a combination of expertise, including physical science (bloodstain pattern analysis, chromatography, chemical fingerprinting), audiology (voice analysis and recording), photography and photomicrography, document examination, ballistics and chemistry. In addition, a good investigator must have excellent communication skills for interrogating suspects. This is particularly true in cases of domestic violence, sexual assault and hate related incidents.