Stuck to the bottom of your shoe is humble dirt that gives away where you've been and what you've been up to. It's up to science to figure out it out. Nature has a fascinating profile of forensic geologist Lorna Dawson, who has used soil to solve decades-old cold cases.
OK, so CSI: Soil probably quite doesn't have the hilarious tech buzzword potential of CSI: Cyber, but there are a lot of high-tech methods behind forensic geology, too. Dawson has been one of those people pushing the field beyond microscopes. For example, she has adapted methods from chromatography and mass spectrometry, which read out the molecular makeup of samples.
Her work helped convict Angus Sinclair of the grisly World's End murders in 1977, in which 17-year-old girls were raped and strangled. Dawson reanalysed soil from the feet of one of the murdered girls, reconstructing her final moments as Sinclair marched her into a field and killed her. Sinclair was finally convicted in 2014.
Now, Dawson is working on soil microbe profiling as an additional method for tracking down crime. The microbes living in soil vary from location to location. If validated in court, the method will give forensic geologists another trick up their sleeves.