A preliminary investigation is an inquiry conducted by law enforcement representatives to gather more information about an allegation. The purpose of the inquiry is twofold: it is designed to determine whether or not a crime was committed and to identify a suspect or confirm a suspect's identity. Using the results of the inquiry, a decision is made about whether or not to move forward with a full investigation, formal accusation, and trial.
The process starts when someone files a complaint. A police officer takes down details from the complainant, taking special note of facts that can be verified and people who may be related to the case. Once a complaint has been filed, a determination about whether or not it is valid must be made to rule out situations in which allegations are clearly false. Then, a preliminary investigation can be conducted.
In the investigation, steps are taken to verify information in the complaint, and to expand upon that information. This can involve collecting evidence, interviewing people, and taking other investigative steps. All of this information is pulled together in a report. The report can indicate whether or not the investigator agrees that a crime was committed and it may identify a suspect.
There may be situations in which there is clear evidence of a crime, but no suspect. A person cannot be accused of the crime because no one has been identified, but officers can continue to investigate. They can also keep information about the crime on file in the event that more information comes in at a future date, allowing them to reopen the investigation and potentially to bring someone to trial.
A preliminary investigation can indicate that a crime occurred and that someone is a suspect, but it may also reveal that there is not enough evidence to move forward with a prosecution. In this situation, a prosecutor may recommend waiting on a trial and continuing to investigate the case to see if evidence can be collected to support the case. This decision is made with the understanding that, while the case could be brought to trial, it would be a fruitless endeavor because the outcome of the trial would inevitably be acquittal.
Complainants can check on the status of a investigation. The officer the complainant meets with usually provides contact information to allow him or her to follow up on the complaint.