London -
A crime-busting test that can reveal the age of a suspect from a drop of blood has been devised by scientists.
The profiling technique can narrow someone’s age to within nine years using tell-tale markers in DNA.
The test - which even works on years-old dried bloodstains - could shed light on unsolved cold cases dating back decades.
It brings closer the day when forensic investigators can piece together identikit pictures of suspects - including their build and eye and hair colour - from a speck of blood, skin or saliva left at a crime scene.
Detectives currently need teeth or bones to work out the age of a suspect or victim.
The molecular biologists who devised the test say it could be put to immediate use. Dr Manfred Kayser, of Erasmus MC University Medical Centre in Rotterdam, said: “It is applicable in situations where only bloodstains are available - which covers a large proportion of crime cases.”
Previous attempts to come up with an age DNA test have had limited success, Kayser told the journal Current Biology.
The test takes advantage of a characteristic of the body’s T-cells, a type of immune system cell which contain tiny loops of DNA known as “single joint TCR excision circles”. The number of these loops declines at a constant rate with age.
The test counts the loops in a small blood sample, then compares this with other extracts of DNA in the sample that are not affected by age. The two pieces of information are then analysed to work out age.
Conventional DNA profiling can only identify persons already known to investigators, because the approach is completely comparative, Kayser said. “This means that if a DNA profile obtained from evidence does not match that of any known suspect, nor anybody in the criminal DNA database, a case cannot be solved. In such situations, information estimated from evidence, such as the age blood test, could help in finding unknown persons.”
The test proved “highly accurate” in placing unknown people into age categories spanning about 20 years, and was found to work on bloodstains which were one and a half years old. “I wouldn’t be surprised if it could be used on bloodstains decades or hundreds of years old,” added Kayser.
The Forensic Science Service welcomed the breakthrough. A spokesman added: “This test does have quite a broad age spectrum at the moment, but it could give additional help.” - Daily Mail