Police: Criminal Investigations

An investigation refers to the process of collecting information in order to reach some goal; for example, collecting information about the reliability and performance of a vehicle prior to purchase in order to enhance the likelihood of buying a good car. Applied to the criminal realm, a criminal investigation refers to the process of collecting information (or evidence) about a crime in order to: (1) determine if a crime has been committed; (2) identify the perpetrator; (3) apprehend the perpetrator; and (4) provide evidence to support a conviction in court. If the first three objectives are successfully attained, then the crime can be said to be solved. Several other outcomes such as recovering stolen property, deterring individuals from engaging in criminal behaviors, and satisfying crime victims have also been associated with the process.

A useful perspective on the criminal investigation process is provided by information theory (Willmer). According to information theory, the criminal investigation process resembles a battle between the police and the perpetrator over crime-related information. In committing the crime, the offender emits "signals," or leaves behind information of various sorts (fingerprints, eyewitness descriptions, murder weapon, etc.), which the police attempt to collect through investigative activities. If the perpetrator is able to minimize the amount of information available for the police to collect, or if the police are unable to recognize the information left behind, then the perpetrator will not be apprehended and therefore, the perpetrator will win the battle. If the police are able to collect a significant number of signals from the perpetrator, then the perpetrator will be identified and apprehended, and the police win. This perspective clearly underscores the importance of information in a criminal investigation.

The major problem for the police in conducting a criminal investigation is that not only is there potentially massive amounts of information available, but the relevance of the information is often unknown, the information is often incomplete, and the information is often inaccurate. Further, to be useful in proving guilt in court (where beyond a reasonable doubt is the standard), the evidence must have certain other qualities, and certain rules and procedures must be followed in collecting the evidence.