Perfect crime is a colloquial term used in law and fiction (especially crime fiction) to characterize crimes that are undetected, unattributed to a perpetrator, or else unsolved as a kind of technical achievement on the part of the perpetrator. In certain contexts, the concept of perfect crime is limited to just undetected crimes; if an event is ever identified as a crime, some investigators say it cannot be called "perfect".
A perfect crime should be distinguished from one that has merely not been solved yet or where everyday chance or procedural matters frustrate a conviction. There is an element that the crime is (or appears likely to be) unable to be solved.
As used by some criminologists and others who study criminal investigations (including mystery writers), a perfect crime goes unsolved not because of incompetence in the investigation, but because of the cleverness and skill of the criminal. In other words, the defining factor is the primary causative influence of the criminal's ability to avoid investigation and reprisal, and not so much the ability of the investigating authority to perform its duties.
Would-be perfect crimes are a popular subject in crime fiction and movies. They include Rope, Double Indemnity, Strangers on a Train, The Postman Always Rings Twice, Witness for the Prosecution, and Dial M for Murder.
A murder committed by somebody who had never before met the victim, has no criminal record, steals nothing, and tells no one might be a perfect crime. According to criminologists and scientists, this casual definition of perfect crime exists. Another possibility is that a crime might be committed in an area of high public traffic, where DNA from a wide variety of people is present, making the sifting of evidence akin to 'finding a needle in a haystack'.
An intentional killing in which the death is never identified as murder is an example of one of the more rigorous definitions of perfect crime. Other criminologists narrow the range to only those crimes that are not detected at all. By definition, it can never be known if such perfect crimes exist. Many "close calls" have been observed, however—enough to make investigators aware of the possibility of a perfect crime.
In March 2009, a jewel theft was described as being close to a perfect crime, in that despite having DNA evidence the police were unable to bring the case to court since the DNA belonged to one of a pair of identical twins, and faced with denials by both, it could not be proven which of the two was the criminal.
- Timmermans, Stefan. Postmortem: how medical examiners explain suspicious deaths, University of Chicago Press, 2006, p. 157. ISBN 0-226-80398-8
- Francis, Charles. Murder By The Bay: Historic Homicide in and about the City of San Francisco. Quill Driver Books. p. 162; 2005; ISBN 1-884995-46-2. Retrieved 2007-10-28.
- "How to commit the perfect murder". Horizon. Season 2007. 2007-05-08.
- Vedder, Clyde Bennett. Criminology: a book of readings, Holt, Rinehart and Winston, 1953, p. 44. "Detectives have said that they have never seen a perfect crime. This is because the only perfect crimes are those in which no one even suspects..."
- The Journal of criminal law, criminology and police science, p. 141, 1962. Northwestern University School of Law, American Society of Criminology, Illinois Academy of Criminology, International Association of Arson Investigators, National District Attorneys Association, National Association of County and Prosecuting Attorneys, Society for the Advancement of Criminology, JSTOR, National Association of Defense Lawyers in Criminal Cases.
- Himmelreich, Claudia (March 23, 2009). "Despite DNA Evidence, Twins Charged in Heist Go Free". Time. Retrieved 2009-05-04.
- Postmortem: How Medical Examiners Explain Suspicious Deaths by Timmermans, Stefan. 380 pages, University of Chicago press; ISBN 978-0-226-80398-2.
- The Perfect Crime and How To Commit It by Jekel, Dr. Pamela L. Jekel; Publisher: Paladin Press Boulder, CO 1982; ISBN 0-87364-237-6.
- Practical Crime Scene Processing and Investigation by Ross M. Gardner; 2004 CRC Press, ISBN 0-8493-2043-7.