20-03-2025
Breakthrough DNA technique could solve hundreds of cold cases
Hundreds of cold cases including murders and rapes could be solved by a new DNA-testing technique which helped catch the killer of a retired postmistress 12 years after she was murdered.
Scientists say Y-STR analysis, which can detect tiny fragments of male DNA, is being underutilised in investigations – despite providing the breakthrough in the case of Una Crown, who was stabbed to death at her bungalow in Wisbech, Cambridgeshire, in January 2013.
David Newton, 70, a retired kitchen fitter, was charged with her murder in 2024 after the Y-STR method was used to match his DNA to samples taken from the 86-year-old widow's bloodied fingernails after she died.
Newton, who had been arrested and released during the original murder investigation when the technique was in its infancy, was found guilty in February 2025. He was jailed for life and ordered to serve at least 21 years in prison.
'Y-STR is such a powerful technique in our fight against violence against women and girls,' said Dr Debbie Sharp, from the Forensic Capability Network (FCN), which coordinates scientific work in policing. 'I think we could solve hundreds more cases.'
Y-STR analysis works by focusing on the characteristics of the Y-chromosome which appears in the DNA of people who are genetically male.
Unlike DNA-17, the standard process commonly used in criminal cases, Y-STR testing is able to pinpoint male DNA when it is mixed in with, and masked by, large amounts of female genetic material, making it particularly useful in some cases of rape and serious sexual assault.
'Absolutely worth the investment'
The technique helped to exonerate Andrew Malkinson, who had been wrongly jailed for a rape he did not commit in 2003. After 17 years in prison, Mr Malkinson was cleared on appeal after DNA evidence implicated another man.
However, Y-STR testing is not as statistically robust as the DNA-17 method. Where a crime scene sample matches a suspect's profile using DNA-17, the likelihood that it is not that person can be as high as one-billion-to-one. Under Y-STR, the probability of a match is typically 1 in 28,000.
Dr Sharp, a forensic biologist, is leading a FCN programme to boost the statistical certainty of Y-STR testing. Under the scheme, scientists are collecting anonymous Y-STR samples from men living in Britain to establish the frequency with which certain features of the Y-chromosome appear in the population.
'Building a UK reference collection will help us to provide much more compelling statistics – not only to help juries make decisions in cases, but also to encourage guilty suspects to plead guilty at an earlier stage,' she said.
The project, known as 'Swab Out Crime', already has 4,000 Y-STR specimens taken from men's saliva – but needs at least 6,000 more.
'We don't even ask donors for their names or their dates of birth,' said Dr Sharp. 'We only ask for information about ethnicity and place of birth for the donor and a couple of their male relatives.'
The long-term aim is to establish a database containing Y-STR profiles from people arrested by police so it can be automatically searched for a potential match with Y-STR obtained from a crime scene or a victim.
The system would operate along the lines of the national DNA database which holds DNA profiles of more than 6 million individuals.
At present, the only way of discovering who an unknown Y-STR profile from a crime belongs to is to swab individual suspects or carry out a mass screening programme.
'We have permission to build the IT capability to collect Y-STR samples from arrestees but we don't have the funding,' said Dr Sharp.
'It's in the millions, but it's absolutely worth the investment.'
