coldcase

A cold case is a criminal investigation that remains unsolved after investigators have exhausted routine leads and the case has moved beyond the period in which it is typically pursued for close resolution. Definitions vary by jurisdiction; many agencies designate a case as cold after a set number of years with no meaningful progress, or when investigative activity has halted for extended periods.

Cold cases are typically reopened when new information emerges, when a suspect is identified, or when advances in forensic science create new opportunities to test evidence. In practice, cold-case work is often carried out by dedicated cold case units or by detectives who re-examine files, re-interview potential witnesses, and seek new leads through public appeals.

Advances in technology have transformed cold-case investigations. DNA analysis, genetic genealogy, improved fingerprint and digital forensics, and data integration across crime databases have led to breakthroughs in some cases. Agencies may use CODIS, national and international databases, and open-source information to link cases or identify suspects.

Notable examples include the arrest and charging of the Golden State Killer in 2018 after DNA profiling and genetic genealogy linked him to several murders, rapes, and other crimes from the 1970s and 1980s. By contrast, other famous cases, such as the Zodiac killings, remain unsolved.

Cold-case work faces challenges, including limited or degraded evidence, scarce resources, and privacy concerns related to genetic genealogy and data collection. While some cases are ultimately solved, many remain open or inactive, continuing to be revisited as new information becomes available.