How to Solve Crimes with Dirt and Chromatography

We’ve all seen CSI and have all marvelled at the ingenuous ways in which the detectives get their man. Of course, that’s a TV show, where fact is often morphed into fiction and techniques are exaggerated – or even completely invented – to inflate the poetry of the storyline.

However, not all of the forensic techniques featured in the show are quite so far-fetched. Of course, soil analysis has been used in criminal cases since long before Sir Arthur Conan Doyle incorporated it into his Sherlock Holmes’ tales. More recently, one of Doyle’s compatriots has combined soil analysis with gas chromatography to take the discipline to a whole new level.

Chromatography Follows the Footprints

Scottish forensic geologist Lorna Dawson entered Edinburgh University in 1977, the same year that a couple of grisly murders were carried out not far from the student accommodation in which she lived. Two young girls were last seen at the World’s End pub in the Scottish capital, walking away with two men – the next day, their bodies were found 8km apart.

While the murders shook Dawson in her first year away from home, she persevered with her studies and eventually specialised in soil analysis. By degrees, she gravitated towards the use of sophisticated soil analysis (employing techniques such as electron microscopy for mineralogy and gas chromatography and mass spectrometry (GC-MS)) in criminal cases.

Eventually, she was drawn back to the very case which had affected her as a student. Using soil samples taken from the feet of the deceased girls, Dawson was able to help prosecutors tie their prime suspect, Angus Sinclair, to the crime scene. Sinclair had previously been tried for the crime after his semen was discovered on the girl’s clothing, but insufficient evidence had less to a collapse of the case.

Now, armed with Dawson’s chromatographic evidence, the court was able to establish a theoretical timeline which completely disproved Sinclair’s alibi and led to him being sentenced for 37 years for the double murder in 2014. The sentence was the longest in Scottish legal history and was made possible by Dawson’s small but incredibly vital contribution.

She continues to propagate the merits of soil analysis in criminal cases around the world, raising the profile of chromatography’s sleuthing abilities and helping to gain some sort of closure for the families of the victims. “Lorna has been instrumental in promoting the new renaissance in forensic geoscience throughout the world,” attests Marianne Stam, recently-retired member of the California Department of Justice. “What Lorna is doing is pioneering new ground, developing methods that others could use and should try more.”

CSI : Chromatography?

Soil analysis is just one of the ways in which chromatography is instrumental in constructing criminal cases against suspects. The article How is Gas Chromatography Used in Forensics? discusses its role in arson investigation and forensic pathology, among other avenues.