Every person has a unique DNA profile and samples from a crime scene can be vital in identifying offenders and ruling out innocent people.
Samples from crime scenes - including bodily fluids and hair –are analysed to build a DNA profile.
Saliva and blood are the most common bodily fluids, but DNA can be found in all living cells including flakes of skin and fingernails.
Unlike fingerprint analysis, which is carried out on site, DNA samples are profiled and matched by specialist agencies such as the Forensic Science Service.
DNA samples from detainees are all processed through the DNA section of the Bureau, who check the validity and quality of the samples before submitting them to the Forensic Science Service. Most of these checks are the same as those applied to detainee fingerprints, so it’s more efficient to keep all this work together.
It may be that the DNA profile or fingerprint cannot be matched to a named person, but the profile and prints are added to the national DNA and fingerprint databases where sooner or later they could be used to detect a crime.