How Much Information Can Chromatography Get from Hair?

At a recent meeting of the American Chemical Society, a team from West Virginia University led by Dr Peter Jackson, announced the latest breakthrough for forensic science — hair analysis. Now you might not think that the announcement is news — but although hair analysis is routinely used for drug testing for employment purposes — but, the forensic testing of hair has had a troubled recent past.

Hair today — free tomorrow

Hair analysis was once one of the main techniques used by the police and prosecutors to bring criminals to justice. Microscopic analysis of hair to reveal the colour, thickness and curvature were used to link suspects to crime scenes. But, many critics of the method argued that the test was too subjective and unreliable.

A review by the US Department of Justice and the FBI found that approximately 90 per cent of testimonies or trial transcripts concerning hair analysis contained errors. In fact, in an FBI press release an FBI Co-Director stated: ‘These findings confirm that FBI microscopic hair analysts committed widespread, systematic error, grossly exaggerating the significance of their data under oath with the consequence of unfairly bolstering the prosecutions’ case.’

But although DNA testing has become the mainstay of criminal investigations, Jackson notes that hairs found at crime scenes might not have enough DNA to allow a viable match, and the DNA might not be registered on the criminal database. And this is where the new technique and chromatography come into play.

Age, sex, weight and BMI — all from hair?

While DNA can identify genetic material, and provide a match to the database, it reveals nothing about the lifestyle of the suspect. But Jackson and his team used liquid chromatography in conjunction with isotope ratio mass spectrometry (LC-IRMS) to identify a whole lot more from samples of hair. LC-MS is a powerful technique with many forensic possibilities — one is discussed in the article, A Simplified Mixed-Mode Sample Preparation Strategy for the LC-MS/MS Analysis of Benzodiazepines and Z-Drugs for Forensic Toxicology.

The team used LC-IRMS to measure the ratio of isotopes in the amino acids found in keratin, the main protein in our hair. The team could identify 15 isotope ratio measurements that could be used to give information about the suspect. They tested their method by collecting hair samples from 20 Jordanian women and 20 US men and women.

The team could predict a person’s BMI with 80 percent accuracy and identify the sex of the donor with 90 percent accuracy. More work needs to be done before we see the process used in CSI — the methodology needs refinement, but LC-IRMS could soon mean hair analysis is back in the dock.