New DNA tool can help catch criminals

Scientists have developed a novel tool that can accurately predict eye, hair and skin colour from even a small DNA samples left at a crime scene or obtained from archeological remains.

The 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 webtool.

The tool is designed to be used when standard forensic DNA profiling is not helpful because no reference genetic data 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 as law enforcement officials or anthropologists, can enter relevant data using a laboratory DNA analysis tool, and the webtool 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 Indiana University - Purdue University Indianapolis (IUPUI) in the US.

"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 coloration," said Walsh.

"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," she said.

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

"With our new HIrisPlex-S system, for the first time, forensic geneticists and genetic anthropologists are able to simultaneously generate eye, hair and skin colour 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 University in Netherlands.