What Is a Cold Case?
The definition of a cold case varies from agency to agency. The National Institute of Justice currently defines a cold case
as any case whose probative investigative leads have been exhausted. In essence, this means a case that is only a few months
old may be defined as being "cold."
Attention continues to be focused on cold cases — or "historical" cases as they are called in many countries outside the U.S.
— due to the popularity of television dramas and the increased involvement and public visibility of family members.
Recent advances in DNA technology also are allowing officials to take a fresh look at these cases. Short tandem repeat analysis allows officials to test samples that, in the past, were too small to examine and to use statistics to confirm that a DNA
profile belongs to one specific person. Using mitochondrial DNA, they can also test hairs (as the Palm Beach County Sheriff's Department did in the case of Kizzy Brooms; see main story)
and unidentified remains that may accompany a cold case as evidence.
Along with these technological advances, the creation of the Combined DNA Index System (CODIS) has improved the chances of
solving cold cases with DNA. Established and managed by the FBI, CODIS allows DNA profiles to be uploaded into a database
and searched against other profiles at the local, state and national levels. There are two main indices in CODIS: the forensic
index, which houses crime scene or evidence DNA samples, and the convicted offender index, which contains profiles for convicted
offenders from all 50 states. CODIS also contains profiles of missing persons and arrestees (if state law permits the collection
of arrestee samples). (For more information on CODIS, see https://www.fbi.gov/services/laboratory/biometric-analysis/codis).
[note 1] Short tandem repeat (STR) technology is a forensic analysis that evaluates specific regions (loci) found on nuclear DNA.
STRs are multiple copies of a short identical sequence arranged in direct succession in particular regions. The variable (polymorphic)
nature of the STR regions analyzed for forensic testing intensify the discrimination between DNA profiles. For example, the
likelihood that any two individuals (except identical twins) will have the same 13-loci DNA profile can be as high as 1 in
[note 2] Mitochondrial DNA (mtDNA) has provided forensic scientists with a valuable tool for determining the source of DNA recovered
from damaged, degraded or very small biological samples. mtDNA is a small circular genome located in the mitochondria, which
are located outside of a cell's nucleus. Most human cells contain hundreds of copies of mtDNA genomes, as opposed to two copies
of the DNA located in the nucleus. This increases the likelihood of recovering sufficient DNA from compromised DNA samples,
and for this reason, mtDNA can play an important role in missing persons investigations, mass disasters and other forensic
investigations involving samples with limited biological material.
Date Created: July 15, 2008