Hair strands could reveal the lifestyle secrets of criminals

Scientists have developed a new forensic technique that is so precise it could be able to determine which one of two genetically identical twins is the heaviest from just a few strands of hair.

The new method is being hailed as a breakthrough that could provide vital clues not just about a person’s weight but also their age, sex, diet and exercise regime – or lack of one – from a smattering of follicles.

Forensic hair analysis was once the darling of criminal investigations and court rooms but has fallen out of favour in recent years after leading to a series of wrongful prosecutions that were later overturned.

Old methods subjective and unreliable

Far from being the objective and concrete arbiter of justice people had hoped, it turned out that follicle analysis was highly subjective and unreliable. A US government review even found that 90 per cent of hair examiners’ testimonies in criminal trials contained incorrect information.

But all that could be about to change after a team of researchers found a way to delve deeper into the chemical composition of hair.
“Who you are, where you’ve been, what you eat, what drugs you take – it all shows up in your hair,” said Dr Glen Jackson, of West Virginia University.

“You could have genetically identical twins, and if one is obese and one is lean, we potentially could tell the difference between their hairs with our method. Depending on the question being asked, the chemical analysis of human hair can provide amazing insights into the life and lifestyle of a person,” he added.

It’s all about the keratin

The technique involves looking at the ratios of different types of atoms contained within the 21 amino acids found in keratin, the primary constituent of hair (which is also found in skin and nails).

The test, which the researchers say is not too difficult to perform, was able to predict a person’s body mass index with between 80 and 90 per cent accuracy.

However, while the new method is highly promising Dr Jackson says more work is needed to boost its library of hair samples and to refine the technique before it can be used in crime labs.

Furthermore, the technique requires several strands of hair from the same person ruling out crime scenes where only a single strand may be available.

The researchers presented their findings to a meeting of the American Chemical Society.

The problem with DNA hair analysis.

The new hair test does not involve any DNA analysis, even though this is the current gold standard in criminal cases. That’s because hairs found at crime scenes often don’t have enough viable DNA in them for analysis, according to Dr Jackson. And even if DNA is available, a matching sample might not be found in existing criminal databases. In addition, DNA only provides a genetic profile of a suspect and reveals nothing about the person’s lifestyle, which could be key to breaking a case.