Cold case

A cold case is a crime, or a suspected crime, that has not yet been fully resolved and is not the subject of a current criminal investigation, but for which new information could emerge from new witness testimony, re-examined archives, new or retained material evidence, or fresh activities of a suspect. New technological methods developed after the crime was committed can be used on the surviving evidence to analyse causes, often with conclusive results.

Violent or major crime


Typically, cold cases are violent and other major felony crimes, such as murder and rape, which—unlike unsolved minor crimes—are generally not subject to a statute of limitations.

Sometimes disappearances can also be considered cold cases if the victim has not been seen or heard from for some time, such as the case of Natalee Holloway or the Beaumont children.

The rate of cold cases being solved are slowly declining, soon less than 30% will be solved per year. About 35% of those cases are not cold cases at all. Some cases become instantly cold when a seeming closed (solved) case is re-opened due to the discovery of new evidence pointing away from the original suspect(s). Other cases are cold when the crime is discovered well after the fact—for example, by the discovery of human remains. Some cases become classified cold cases when a case that had been originally ruled an accident or suicide is re-designated as murder when new evidence emerges.

The John Christie murders is a notable case when Timothy Evans was wrongly executed for the alleged murders of his wife and child. Many other bodies were later found in the house where they lived with Christie, and he was then executed for the crimes. The case helped a campaign against capital punishment in Britain.

Identifying a suspect
A case is considered unsolved until a suspect has been identified, charged, and tried for the crime. A case that goes to trial and does not result in a conviction can also be kept on the books pending new evidence.

In some cases, a suspect, often called a "person of interest" or "subject" is identified early on but no evidence definitively linking the subject to the crime is found at that time and more often than not the subject is not forthcoming with a confession. This often happens in cases where the subject has an alibi, alibi witnesses, or lack of forensic evidence. Eventually, the alibi is disproved, the witnesses recanted their statements or advances in forensics helped bring the subjects to justice.

Sometimes a case is not solved but forensic evidence helps to determine that the crimes are serial crimes. The BTK case and Original Night Stalker (the latter pending trial as of April 24, 2018) cases are such examples. The Texas Rangers have established a website in the hopes that it shall elicit new information and investigative leads.

Tunnel vision
Sometimes, a viable suspect has been overlooked or simply ignored due to then-flimsy circumstantial evidence, the presence of a likelier suspect (who is later proven to be innocent), or a tendency of investigators to zero in on someone else to the exclusion of other possibilities (which goes back to the likelier suspect angle)—known as "tunnel vision".

Improvements in forensics
With the advent of and improvements to DNA testing/DNA profiling and other forensics technology, many cold cases are being re-opened and prosecuted. Police departments are opening cold case units whose job is to re-examine cold case files. DNA evidence helps in such cases but as in the case of fingerprints, it is of no value unless there is evidence on file to compare it to. However, to combat that issue, the FBI is switching from using the Integrated Automated Fingerprint Identification System (IAFIS) to using a newer technology called the Next Generation Identification (NGI). Other improvements in forensics lie in fields such as:


 * Digital Forensics one application of which is to recover hidden or deleted data.
 * Ballistics Analysis which involves the evaluation of ammunition and firearms to determine which weapon might have been used in a crime.
 * Forensic Anthropology which analyzes skeletal remains to determine their cause of death or any other relevant information.
 * Mobile Forensics and Social Media which, since their creation, have had increased involvement in any police case cold or not.
 * Forensic Psychology which can be used to analyze crime scenes and identify suspect profiles.
 * Facial Recognition which has been used to identify suspects based on their facial features.
 * Artificial Intelligence (AI) which is used in all of the above systems to help analyze data and information from crime scenes.

Famous criminal examples
The identity of Jack the Ripper is a notorious example of an outstanding cold case, with numerous suggestions as to the identity of the serial killer. Similarly, the Zodiac Killer has been studied extensively for almost 50 years, with numerous suspects discussed and debated. The perpetrators of the Wall Street bombing of 1920 have never been positively identified, though the Galleanists, a group of Italian anarchists, are widely believed to have planned the explosion. The burning of the Reichstag building in 1933 remains controversial and although Marinus van der Lubbe was tried, convicted and executed for arson, it is possible that the Reichstag fire was perpetrated by the Nazis to enhance their power and destroy democracy in Germany.

Film

 * In the movie Max Payne, Detective Max Payne works in Cold Case, NYPD

Literature
The phrase "Cold Case" is found in a number of story and book titles. Examples include:
 * L.L. Bartlett (2010). "Cold Case". A Jeff Resnick Mystery. . Polaris Press. This short story inspired the fourth Jeff Resnick book, Bound by Suggestion.
 * True crime.
 * A children's book/mystery.
 * An urban novel.
 * An education and reference book.

Music

 * Cold Case Files (2008) and Cold Case Files Vol. 2 (2012) are compilation albums by the rap group Onyx
 * "Cold Case Love" is a song on Rihanna's Rated R album, released November 23, 2009 on the Def Jam label
 * "Stella: The Cold Case" is an EP by Aafke Romeijn

Television

 * The Canadian television series Cold Squad (1998–2005), the British television series Waking the Dead (2000–2011) and the American television series Cold Case (2003–2010) all follow groups of fictional homicide detectives who investigate cold cases. They are set in Vancouver, London and Philadelphia, respectively.
 * Cold Case Files (1999–2006) is a documentary-style television series recounting actual solved cold cases.
 * New Tricks is a BBC series revolving around retired CID officers acting as consultants to serving officers and investigating unsolved cold cases.
 * ''Unforgotten is a ITV, DCI Cassie Stuart (Nicola Walker) and DI Sunny Khan (Sanjeev Bhaskar), as they solve cold cases of disappearance and murder.

Video game

 * Chase: Cold Case Investigations - Distant Memories is a video game about two detectives of the Tokyo Metropolitan Police Department's cold case unit, Shounosuke Nanase and Koto Amekura.
 * Cold Case Inc - Cold Case Inc is an innovative online platform that offers immersive and interactive unsolved cold case file games.