Where is your DNA?

Where is your DNA?

By Sian Cooper

Published: 13 Mar 2026

You may know that the Police can take DNA mouth swabs from most people who they arrest without their permission. But what about the DNA tests that you have voluntarily given to companies such as Ancestry.com and 23andMe? Can the Police access and use this data? 

Hundreds of thousands of people in the UK have paid to provide their genetic material to genealogy websites to explore their family history, connect with relatives or even to find out information about their genetic health markers. There is a common myth that the Police can easily access this data. Clients often ask us whether law enforcement can search commercial DNA databases whenever they wish, so it is important to explain how the law actually works.

Companies such as Ancestry.com and 23andMe do what is known as ‘genetic genealogy’. This is the application of DNA analysis and traditional genealogy to infer relationships between individuals. Those who are closely related share segments of DNA and the more distant the relationship, the less DNA they will share. We share 50% of our DNA with a parent but by the time we reach a third cousin, we share, on average, only around 0.8% of our DNA. The level of shared DNA is used to suggest a level of familial relationship.

So why does this matter in criminal investigations? Genetic genealogy analysis requires high-quality DNA to be recovered from a crime scene. This essentially limits its use to semen, saliva or blood. In the USA, an assessment of 200 cases was carried out for the suitability of a genealogical approach and around 35% were found not to be suitable. Genetic genealogy has been used in the USA and resulted in the capture of the ‘Golden State killer’ in 2013, who had committed a series of murders, rapes and burglaries between 1974 and 1986. In the UK, a related approach contributed to solving the murder of Melanie Road more than 32 years after her death, when her killer’s daughter appeared as a partial match on the UK Police DNA Database. Her case has since been documented in retired Detective Superintendent Julie MacKay’s book, To Hunt a Killer.

Familial searching has been used for UK serious crimes since 2003 using standard DNA profiles and ranking the likelihood of a familial relationship between an unknown individual who has left DNA at a crime scene and individuals on the National DNA Database.   The technique used can only identify parents, children and siblings and the success rate is only around 20%.

So, can the Police access your DNA data from these websites? Yes, but only if they have followed a legal process, such as applying for a Court Order. Databases are not available for the Police to simply browse and your DNA data will not simply handed over because the Police have asked. Article 8 of the Human Rights Convention protects private and family life and sets a high threshold for access. GDPR also treats DNA as special category data, which gives it stronger protection. These legal safeguards, combined with cost and reliability issues, mean that genetic genealogy plays only a limited role in UK policing.