A new system developed by Dutch, American, and Polish forensic scientists combines genetic testing and computer modeling to create an accurate “sketch” of a individual’s coloration – a breakthrough that will enable detectives to build profiles of unidentified criminals, and archaeologists to reveal characteristics of discovered human remains.
First introduced to the public in the early 2010s, genetic testing protocols known as forensic DNA phenotyping (FDP) can predict an individual’s hair and eye color based on analysis of trace amounts of DNA left at crime scenes. The nascent field was initiated so that investigators gather information about suspects and victims in instances where no reference DNA is available for comparison.
One FDP platform known for its high level of accuracy is the HIrisPlex, created by researchers at the Erasmus MC University Medical Centre in the Netherlands in 2014. The system first uses a DNA assay to look for specific genetic variations, called SNPs, within genes associated with hair and eye pigmentation. The results can then entered into a free online tool that calculates how the SNPs interact to generate a person’s most likely real-life coloration. Because the model is open-access, any lab with SNP test data can utilize it.
Though other systems claim to also predict characteristics such as face shape or height, the results must be taken with a grain of salt because these features are mediated by complex interactions in many genes, whereas the ones that determine brown hair vs blonde are fairly straightforward.
And until now, FDP methods for determining skin color were also unreliable.
As described in the journal Forensic Science International: Genetics, the team behind HIrisPlex has demonstrated that their upgraded system, HIrisPlex-S, is the FDP capable of simultaneously detecting hair, eye, and skin color from DNA samples.
"We have previously provided law enforcement and anthropologists with DNA tools for eye color and for combined eye and hair color, but skin color has been more difficult," study co-director Susan Walsh said in a statement.