Keratin a clue to nailing sex crimes

A new forensic technique that tells scientists which cells come from which parts of the body could help solve sex crimes, its developers say.

A New Zealand PhD student has found a unique way of identifying whether cell samples collected for DNA testing come from the skin, mouth or vagina.

The development is the work of research student Claire French from the University of Auckland. She said: “All it really involves is a couple of stains and some microscope slides of the cell samples and you get some lovely different coloured cells.”

Currently, DNA from cells found at a crime scene can link a person to the crime but cannot provide evidence about which part of the body the cells came from.

The technique French has developed involves staining epithelial cells, the outer layer of body surfaces and organs, which are easily shed or secreted. The stain reveals different colours, corresponding to the presence of the protein keratin.

“Vaginal cells don’t express the protein, giving a characteristic yellow colour. But skin cells and some mouth cells do, so they stain magenta and red,” said French.

Sue Vintiner, a forensic scientist with New Zealand’s Environmental Science and Research (ESR), believes the technology could have practical applications.

She said: “I’ve been involved in cases where we’ve been unable to scientifically prove that an object has been used to violate someone in a sexual assault or whether it was just touched by the alleged victim. Claire’s work could change that.”

Developers are interested in harbouring the technology into a portable, histological staining kit for routine use at crime scenes and in forensic laboratories.

French’s research will be presented at the national European Academy of Forensic Sciences conference and has received strong support from the New Zealand Police.

Claire’s findings have also earned her New Zealand’s McDiarmid Young Scientist of the Year Award.