Every record in the NDNAD is derived from a sample of human material, usually saliva or hair. Where possible, samples are also collected from crime scenes. Specialized laboratories process the samples and extract the DNA profile.
The rules governing how samples are collected, and what happens to them next depends on where in the UK you live. In England and Wales, the police can take a sample without consent from anyone arrested for a recordable offence*. Both the profile and the original sample are kept indefinitely, even if the person is innocent. Volunteers who give permission for their profile and sample to be retained cannot change their minds later.
DNA profiles and samples are police property and are used to help solve crimes. Special permission is required to use them for any other purpose such as genetic research.
*Almost all criminal offences are recordable, including minor offences such as begging or being drunk and disorderly. Most recordable offences can lead to a prison sentence.
The situation in the UK
Scotland and Northern Ireland (NI) have their own national databases, but export profiles to the NDNAD. NI processes are similar to England and Wales, but in Scotland:
- samples are only taken in connection with serious crimes
- both profile and sample are destroyed if the person is not charged or convicted, and can be requested back from the NDNAD
- volunteers can withdraw their permission
