The next time you leave your DNA behind be forewarned that you are now not only leaving your biological fingerprint behind for prying eyes, but also leaving evidence of what color your hair and eyes are. Until the mid-1980s, DNA at a crime scene went largely unchecked due to lack of technology to search it out. And for the last two decades, in order for a crime scene detective to match DNA to a suspect, samples had to be taken from possible matches.
But now, according to a team of researchers, led by professor Manfred Kayser of Erasmus University Medical Center
in Rotterdam, the Netherlands, a new forensic test can predict both the hair and eye color of a possible suspect using DNA at a crime scene. The team said it could provide valuable leads in cases where suspects cannot be identified through DNA profiling
The test, called the Hirisplex system, could allow crime scene investigators to narrow down a large group of possible suspects, making it easier to pinpoint the perpetrator. Details of the research appear in the journal Forensic Science International: Genetics.
Predicting phenotypes is quickly becoming an emerging field in forensics. The current approach, genetic profiling, involves comparing crime scene DNA to possible suspects or to a database of stored profiles. Genetic profiling relies on the person either being among a pool of suspects identified by police or having their profile previously stored.
The Hirisplex approach could be very useful in cases where a perpetrator is completely unknown to the authorities, said Kayser.
The test "includes the 24 currently best eye and hair color predictive DNA markers," Kayser said in a press release. "In its design we took care that the test can cope with the challenges of forensic DNA analysis such as low amounts of material."
"The test is very sensitive and produces complete results on even smaller DNA amounts than usually used for forensic DNA profiling."
Kayser told BBC News' Paul Rincon that the research article outlines everything needed
to establish the test in a forensic lab, but that the team was also in touch with industry regarding their knowledge about hair and eye color prediction.
The test system includes the six DNA markers previously used in a test for eye color known as Irisplex, combining them with predictive markers for hair.
To prove the test actually works, the researchers used the Hirisplex system to predict hair color phenotypes in a sampling of three European populations. On average, the prediction accuracy was 69.5 percent for blonde hair, 78.5 percent for brown, 80 percent for red hair, and 87.5 percent for black hair.
The team said the analysis on worldwide DNA samples suggested the results would be similar regardless of geographic ancestry. The team were also able to determine whether a brown-eyed, black-haired person was either of European or non-European origin with 86 percent accuracy.
The findings were also outlined at the sixth European Academy of Forensic Science
conference in The Hague this week.