A cold hit refers to an instance where one or more connections are made between a crime victim, a perpetrator, and/or a crime scene in the absence of a current investigative lead (i.e., a cold case ).
In October of 1998, the FBI established the National DNA Index System (NDIS ), the primary purpose of which was to make it possible for public sector forensic laboratories throughout the United States to electronically share and compare DNA samples and profiles. The overarching goal of this linkage system is to connect unsolved serial violent crimes to one another and to known violent offenders (particularly to known sex offenders).
In July of 1999, the FBI announced that the new system had produced its first successful cold hit, linking six unknown subject sexual assault cases in Washington, D.C. with three sexual assault cases then being investigated by the Sheriff's Office in Jacksonville, Florida. Shortly thereafter, the forensic laboratory of the Florida Department of Law Enforcement announced that it had positively identified Leon Dundas (deceased) as the perpetrator in all six cases, based on their DNA analysis of a sample of the offender's blood .
CODIS , an acronym for the FBI Crime Laboratory's Combined DNA Index System, provides the framework for the Cold Hit programs. CODIS combines computer technology with forensic science to create a highly effective tool for linking, and potentially solving, violent crimes. Through CODIS, local, state, and federal forensic laboratories can compare and exchange DNA profiles.
The federal government established a series of grants for individual states' development of cold hit programs, in order to facilitate intra-state DNA database development and to defray equipment, administrative, and human resource costs during lab set up. In addition, forensic labs are funded in order to compensate for costs involved in screening external (not from within their own labs) DNA profiles for comparison with existing evidence and confirming hits on unsolved or suspectless sexual assault cases or violent crimes.
In addition to CODIS and NDIS, a website system within each state and across the nation exists for tracking the progress of each evidence kit from the time it enters the DNA analysis system through resolution. The Cold Hit Website system, which can be accessed by individual forensic labs, can be used to generate statistical reports as well as to track case status. Currently, forensic laboratories across all 50 states, Puerto Rico, and the U.S. Army participate in NDIS and the Cold Hit Program.
see also Blood, presumptive test; Bloodstain evidence; Chemical and biological detection technologies; Cold case; Commercial kits; Decomposition.