Researchers have developed a novel web tool that can accurately predict eye, hair and skin colour from even a small DNA sample, an advance that can be used when standard forensic profiling is not helpful.

The "HIrisPlex-S DNA test" system is capable of generating all three pigment traits from human biological material 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.

"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 Susan Walsh, forensic geneticist at the Indiana University-Purdue University Indianapolis in the US.

Users, such as law enforcement officials or anthropologists, can enter relevant data using a laboratory DNA analysis tool, and the web tool will predict the pigment profile of the DNA donor. "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 coloration.

"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. The results are published in the journal, Forensic Science International: Genetics. The innovative high-probability and high-accuracy complete pigmentation profile web tool is available online without charge, the researchers said.