The police investigation is a key part of the criminal justice system and it can take days, weeks or even a year to complete. It involves a variety of people including officers, detectives and prosecutors. The way a crime is investigated will differ depending on the severity of the incident. If a crime is particularly sensitive or serious, it will be allocated to a detective or other specialised officers.
The first thing that police do when they receive a report of an incident is assess the situation. They do this by evaluating the threat to life and safety. During this initial assessment they will decide whether to deploy an officer and what action they will take. They will also gather information from the person who has reported the incident and determine if they are a victim or witness.
Throughout the investigation police officers will collect physical evidence from the scene of a crime and record and document each piece of evidence. This includes collecting blood samples and taking photos. They will also look at electronic data like cell phone and computer records. All this is referred to as a ‘suite of evidence’ and it forms the basis for any prosecution later on. Police must ensure that there is an unbroken chain of custody to protect evidence from being tampered with.
As the investigation continues, officers will interview witnesses and suspects. The interviews are structured and designed to extract useful information. This is often done through body-worn cameras and is recorded. The interviewees will be asked to sign a statement and can be compelled to answer questions. They are entitled to have representation (a union representative or lawyer) during the interview if they wish.