Cold case

A cold case is an unresolved criminal investigation that has received little or no recent investigative activity. It may be reopened when new evidence, technology, or investigative leads emerge.

Cold case unit: A law-enforcement team that reviews unresolved investigations and develops new leads. Dedicated teams can reexamine cases that routine investigative work no longer advances.
Golden State Killer: The unidentified serial offender who committed crimes in California from 1974 to 1986 before being identified as Joseph James DeAngelo. Investigative genetic genealogy helped identify the offender decades after the crimes.
Victimology: The study of victims, victimization, and the social and institutional responses to them. Long-running investigations affect families as well as the people directly harmed by crime.
Active investigation: A current inquiry in which investigators are pursuing leads and gathering evidence. A cold case differs chiefly in the lack of recent investigative activity, not necessarily in its seriousness.
Forensic DNA analysis: The examination of biological evidence to identify or compare genetic profiles for legal investigations. New or improved DNA testing can extract leads from evidence collected years earlier.
Murder of Hae Min Lee: The 1999 killing of a Baltimore high school student that became the subject of the Serial podcast and prolonged legal disputes. The case illustrates how renewed public attention can coexist with contested evidence and unresolved questions.
Wrongful conviction: A conviction of a person who did not commit the crime or was not legally responsible for it. Reopening an investigation can expose mistaken conclusions as well as identify new suspects.
Unsolved crime: A crime for which no perpetrator has been identified or no legal resolution has been reached. An unsolved crime may still be actively investigated; cold case describes a narrower investigative status.
Forensic genealogy: The use of genetic data and family-history research to identify people related to an unknown DNA contributor. Investigators can use genetic relatives to generate leads when a direct database match is absent.
Bear Brook murders: The killings of four people whose remains were found in barrels in New Hampshire between 1985 and 2000. Forensic genealogy helped identify victims and connect the crimes to a perpetrator.

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