Recent criminal cases such as the “Torso in the Thames”; “Lady in the Lake” and murders of Holly Wells and Jessica Chapman all relied heavily on evidence provided by a variety geoscientists. So how can mineralogy, geophysics and geomorphology assist in criminal investigations?
It was 101 years ago that Hans Gross (an examining magistrate) published a handbook for his colleagues outlining types of trace evidence useful in criminal prosecutions. In this, he included soils, rock dust and paints and thus gave legal weight to ideas that had been aired only in popular stories such as Sir Arthur Conan Doyle's Adventures of Sherlock Holmes. The adherence of particles from a scene of crime on suspect's clothing and footwear then became part of established criminal investigation, embodied in Edmond Locard's Exchange Principle “whenever two objects come into contact, there is always an exchange of material”. The champion of forensic geology (what we in the NW Europe would term geoscience) for over 30 years has been Raymond Murray, embodied in “Evidence from the Earth: Forensic Geology and Criminal Investigation” (Murray, 2004). Research in the School of Geography at Queen's is currently focussing on the geophysics of graves, the detection and excavation of illegal toxic waste dumps and the spatial analysis of criminal activity using GIS.
The application of remote sensing, geophysics, landscape change and GIS have had huge impacts on criminal investigations. Remote sensing techniques such as thermal and infrared imaging are now standard in search methodologies. Many geophysical techniques have been tested in the search and definition of objects buried illicitly. Perhaps the most widely used is ground penetrating radar, or GPR, which does not rely on metallic objects to be successful. Most GPR applications have been over loose ground (see the case studies in Ruffell & McKinley, 2004). However, GPR is now deployed from helicopters and from boats. We have recently been experimenting with novel methods of deriving data in freshwater environments in order to better inform the searches for victims of drowning and body deposition. GIS is used to analyse crime patterns at various scales, with a view to prediction and police resources. Other social factors such as street layout, housing type, and deprivation can be combined using GIS to assist planners.
At the micro-scale, the tried and tested techniques of sediment petrography developed by Gross and scientists like Georg Popp some 100 years ago are still used. Other methods such as soil density column and particle size analysis find periodic favour before being denigrated as unsuitable. The point is, the golden chalice of a single soil fingerprinting technique does not exist, but the multi-proxy or conjunctive method already does. Thus in a case involving the School of Geography at Queen's, of a body weighed down with slabs of conglomerate, in order to provide a comparison to conglomerate found at the suspect's house, hand-specimen, thin section, clast petrography, particle size, and cement isotope analyses were all used. Thus in court, multiple analyses stand a better chance of being accepted by judge or jury than a single method. In a recent case, a suspect power-hosed his boots with exactly this intention. Whilst this removed most soil from the exterior, he was not aware that in running through a stream during his escape, diatoms that were unusual to that stream had been captured in the fabric of the shoe, indicating he had been on the escape route rather than his alibi location. In another recent case of arson, spent and unspent matches were found at the scene and were required to be compared to those found at a suspect's house. Match-head mineralogy, matchstick thin sections and the isotopic content of the matchstick wood were analysed by staff in both Geography and Environmental Engineering at Queen's (in conjunction) to show that the matches did not compare.
References – recommended reading
Murray, R.C. 2004. Evidence from the Earth: Forensic Geology and Criminal Investigation. Mountain Press Publishing, Missoula.
Ruffell, A. & McKinley, J. 2005. Forensic geoscience: applications of geology, geomorphology and geophysics to criminal investigations. Earth Science Reviews , 69 , 235-247.