Murder book is a colloquial term used in the United States to describe the file on an open homicide investigation. During a homicide or suspected murder investigation, law enforcement officials collect information relative to solving the case. That information, including crime scene photographs, notes or observations of responding officers and investigators, forensic reports, and suspect details, is compiled into a single file, otherwise known as a murder book. Other pertinent information regarding the criminal investigation, such as witness statements and copies of any executed search warrants, may also be found in the file.
In referencing a murder book, investigators typically mean a single case file, although the term may reference multiple files depending on the context in which the term is used. When dealing with multiple murders, such as the case with serial killings, multiple files or murder books are maintained individually for each crime. Although separate files are maintained, the term murder book may become a collective term to mean all the individual files on cases suspected of having a common perpetrator or perpetrators.
The purpose of a murder book is to create a paper trail of records on a given murder investigation. In short, a murder book documents each stage of the investigatory process into a particular homicide case. The file begins when a murder is reported and ends when a suspect is arrested and charged with the murder. All documentation, including references to physical evidence, is noted in the case file. Throughout the investigation, law enforcement continues to add to the file, as well as use the file contents to help the investigation progress to completion.
Upon completion of an investigation, when a suspect is arraigned and charged with the homicide, the murder book and its contents are forwarded to prosecutors as part of the body of evidence. Crime scene photographs and results of forensic testing may then appear in court as part of the prosecutor’s presentation to the judge or jury. Likewise, witness statements taken at the time of the investigation and included in the file provide information for the prosecutor to develop a witness list for court testimony. Other documentation and information contained in the murder book may also be entered into evidence, depending on the source and validity of such documents.
In the event a suspect is not found or enough evidence amassed to warrant charges, the case remains open. The murder book on such a case remains with law enforcement. After a certain period of time, unsolved cases become cold in terms of clues and the corresponding information collected becomes a cold case file. Cold case files are simply murder books on cases that have seen no new developments in a year or more.