Police investigation involves gathering and examining evidence to support an allegation of criminal activity. This is often done by detectives, but police officers who are trained in criminal investigation can also carry out investigations.
The first step in any police investigation is to visit the scene of a crime or reported incident. Officers will be asked to look for any physical evidence that might help them identify the perpetrator and find out what happened. This may involve going to a home and looking for bloodstaining, fibres, footprints, photographs and more. They will also take samples to be tested by forensic experts.
They may interview anyone who knows anything about the offence. This could include witnesses, family members and alleged offenders themselves. It is important to remember that it is illegal to tamper with any evidence, so the police will try to be respectful and discreet when talking to people involved in an investigation.
A prosecutor may direct police regarding who should be interviewed and the types of questions to ask. This can be especially helpful when a case involves children or vulnerable adults.
The police will work aggressively until they have interviewed everyone who should be contacted, all relevant records have been reviewed and nothing more can be learned from the scene of the crime or reported incident. If an alleged offender is arrested this will usually be done by a warrant unless they are known to be hiding or have shown a lack of co-operation with police.