How many cold cases can DNA evidence solve?
Theoretically thousands, as that is the number of old cases now being reviewed by the Forensic Science Service (FSS). In reality, far fewer, at least in murder cases. The UK has a high rate of success in solving murders, so there are a limited number of unsolved cases where DNA would help; only 1% of all crime scenes yield samples from blood, semen, saliva and hair. However, in other cases, particularly rapes and sexual assaults, there are likely to be an increasing number of reopened cases. Currently everyone arrested who has a DNA sample taken is put on the national database, which has nearly 4 million people on it, along with nearly 400,000 crime scene samples. As the database grows, a controversial issue in itself, so do the chances of matching criminal to crime. A Home Office report last year suggested that police get about 3,000 matches a month, although those are almost all for current rather than “cold” cases. New techniques and developments in existing techniques by the Birmin
