An international team, led by scientists from the School of Science at IUPUI and Erasmus MC University Medical Center Rotterdam in the Netherlands, has developed a novel tool to accurately predict eye, hair and skin colour from human biological material — even a small DNA sample — left, for example, at a crime scene or obtained from archaeological remains. This all-in-one pigmentation profile tool provides a physical description of the person in a way that has not previously been possible by generating all three pigment traits together using a freely available web tool.

The tool is designed to be used when standard forensic DNA profiling is not helpful because no reference DNA exists against which to compare the evidence sample.

The HIrisPlex-S DNA test system is capable of simultaneously predicting eye, hair and skin colour phenotypes from DNA. Users, such can enter relevant data using a laboratory DNA analysis tool, and the web tool will predict the pigment profile of the DNA donor.

"We have previously provided law enforcement and anthropologists with DNA tools for eye colour and for combined eye and hair colour, but skin colour has been more difficult," said forensic geneticist Susan Walsh from IUPUI, who co-directed the study. "Importantly, we are directly predicting actual skin colour divided into five subtypes — very pale, pale, intermediate, dark and dark to black — using DNA markers from the genes that determine an individual’s skin colouration. This is not the same as identifying genetic ancestry. You might say it’s more similar to specifying a paint colour in a hardware store rather than denoting race or ethnicity.

"If anyone asks an eyewitness what they saw, the majority of the time they mention hair colour and skin colour. What we are doing is using genetics to take an objective look at what they saw," Dr Walsh said.

The innovative high-probability and high-accuracy complete pigmentation profile web tool are available online without charge.

"With our new HIrisPlex-S system, for the first time, forensic geneticists and genetic anthropologists are able to simultaneously generate eye, hair and skin color information from a DNA sample, including DNA of the low quality and quantity often found in forensic casework and anthropological studies," said Manfred Kayser of Erasmus MC, co-leader of the study.

The study has been published in the journal Forensic Science International: Genetics.

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