As crime detection and prevention experts, police investigators navigate a diverse array of investigative techniques, including interrogation, search warrants, crime scene analysis, forensic sciences and more. They also work closely with prosecutors to ensure that case elements are ready to withstand the rigorous burden of proof required for a conviction. This collaboration helps prosecutors prepare for preliminary hearings, grand jury sessions and the trial itself.
When a criminal incident occurs, first-arriving officers complete a primary assessment to locate and contain potential threats and protect the safety of witnesses. They then begin documenting the scene and collecting evidence in a systematic manner. Prosecutors depend on these investigatory efforts to help them build strong cases.
Police investigators are trained to be highly observant and to collect physical and forensic evidence in an objective manner. However, their jobs can be emotionally challenging. For example, if a victim/survivor reports an assault or homicide, they may be interviewed by a detective who has to record their feelings. While this is necessary, it can be difficult to standardize (and even more so when the victim/survivor reveals details about their sexuality or emotional trauma).
After an arrest, investigators put together a file for prosecutors. This includes witness statements, a summary of direct evidence and expert analyses. In some jurisdictions, investigators also submit a request to the Public Prosecutor for advice about what charges should be brought. If the crime involves a child, the police may need to contact a child protection agency such as Children’s Aid Society (CAS). This is to ensure that a CAS worker can be present when a victim/survivor is interviewed by police.