The analysis of human DNA has been progressing quickly over the past few years, allowing forensic experts to match a criminal’s DNA with forensic matter found at the scene of a crime. Called genetic profiling, its only issue is that it either relies on the criminal being one of a pool of suspects, or it relies on a sample of his DNA already being stored in the national DNA database.
For example, there have been a number of unsolved cases that have been reopened and, after genetic profiling, the criminal has been tracked down. In the case of the Yorkshire Ripper hoaxer, who managed to deflect police officers from catching the real Ripper for some time, he was eventually tracked down when, in 2005, the case was reopened. Experts were able to take a sample of DNA from the envelope of a letter he had sent and it matched the DNA of one John Humble, whose DNA had been taken following a minor offence a few years before.
Unfortunately, in the case of criminals who are not already known, or are not readily available for checks, the situation is much more complicated and the chances of being able to track down the right person were not high in the past. Nevertheless, as technology advances, criminal justice professionals are being armed with new ways of fighting crime. One of the latest advances is the ability to predict hair and eye color from DNA, which enables them to narrow down a group of potential suspects. This type of test belongs to a branch of forensic biology called Forensic DNA Phenotyping.
Professor Manfred Kayser from Erasmus University Medical Center in Rotterdam led the study into this latest forensic test, which was published in the journal Forensic Science International: Genetics. As a BBC article on the subject explains, a test already in existence called IrisPlex, which includes six DNA markers used to predict eye color, has been combined with predictive markers for hair. As Professor Kayser said, this "includes the 24 currently best eye and hair colour predictive DNA markers. In its design we took care that the test can cope with the challenges of forensic DNA analysis such as low amounts of material."
Called HIrisPlex, the combined system was tested on 1551 individuals from three European countries. The prediction accuracy “was 69.5% for blonde hair, 78.5% for brown, 80% for red and 87.5% for black hair colour.” It also proved possible to differentiate between two people of different racial make-up, who both had brown eyes and black hair.
The HIrisPlex test will only be necessary if all other avenues have been explored and will no doubt be expensive to carry out, but in cases where there are no leads, it could prove to be invaluable. In time, the accuracy level will hopefully also increase, allowing forensic experts to be more precise when offering data to investigating officers, even when working with tiny amounts of DNA.