Police investigate a variety of incidents that involve criminal activity. Investigations are undertaken by detectives, and are an essential part of the police service’s ability to protect people from harm, reduce crime and fear of crime and bring offenders to justice.
Every investigation is different, and the scope of an investigation depends on the type of offence being investigated. The more serious the case, the greater the level of resource committed to an investigation. Police investigations may take days, weeks or even years to complete depending on the complexity of the case and the amount of evidence required to support a prosecution.
Initially at a scene of a crime, investigators will interview witnesses and collect any physical evidence that is available. This evidence is then sent to a laboratory for analysis. Each piece of physical evidence must be carefully recorded and documented, so that it can be presented at trial with an unbroken chain of custody.
A police investigator will also examine any CCTV or photographs and interview a suspect and anyone else who can provide information to help identify them. In doing so, they must always be aware of their duty to ensure that they do not inadvertently breach the suspect’s civil or human rights.
The police will use their knowledge of the modus operandi (the methods professional criminals tend to use) and other intelligence to advance their investigation. For example, they might compile lists of known criminals with aliases and arrest warrants, secondhand-shop and pawn shop records, laundry and dry cleaners’ marks and other public and private databases.