On February 20, 1949 Mrs. Henrietta Helen Olivia Roberts Durand-Deacon, a sixty-nine-year-old wealthy widow, disappeared from the Onslow Court Hotel located in South Kensington, London. The police interviewed the residents, and soon forty year-old John George Haigh became a suspect, as he was the last person to have seen the woman alive and was known already to the police for crimes of fraud and thievery. He led the police to an old storeroom on Leopold Road in Sussex, where they discovered strange and suspicious tools - a revolver, some rubber protective clothing and three containers filled with sulphuric acid.
Soon afterwards, during an interrogation, Haigh suddenly confessed to an incredible crime "Mrs. Durand-Deacon no longer exists. She has disappeared completely, and no trace of her can ever be found again. I have destroyed her with acid. You will find the sludge which remains on Leopold Road. But you can't prove murder without a body." Fortunately Haigh ignored one important fact in his euphoria: the law doesn't require a body to incriminate him - it requires a corpus delicti- the evidence that a murder happened.
The eminent forensic pathologist Keith Simpson examined carefully the ground at the supposed crime scene. He noted something unusual, a small pebble which he described as follows: "It was about the size of a cherry, and looked very much like the other stones, except it had polished facets."
This pebble was unlike other rocks found at the site. Soon Simpson realized that he had found the evidence to prove the murder. The pebble was a gallstone from poor Mrs. Durand-Deacon. Gallstone can form from calcium-salts and organic substances in the gallbladder, it is the organic sludge that covers them that protected the pebbles from being dissolved in the acid.
John George Haigh, who was ultimately suspected of committing an entire series of murders, was sentenced to death.
This forensic case was an unusual example of how a pebble can help solve a crime. However already in the mid of the 19th century people realized that rocks, soils and the science of geology could be used to reconstruct a crime and provide circumstantial evidence to connect a suspect with the crime scene. An 1856 one issue of the magazine "Scientific American" reported the "Curious Use of the Microscope" to help clarify a case of thievery:
"Recently, on one of the Prussian railroads, a barrel which should have contained silver coin, was found, on arrival at its destination, to have been emptied of its precious contents, and refilled with sand. On Professor Ehrenberg, of Berlin [1795-1896, famous zoologist and geologist] from Leipzig in, being consulted on the subject, he sent for samples of sand from all the stations along the different lines of railway that the specie had passed, and by means of his microscope, identified the station from which the interpolated sand must have been taken. The station once fixed upon, it was not difficult to hit upon the culprit in the small number of employees on duty there."
Fig.1. A small array of soil and unconsolidated sediment samples collected by me on a short field trip - every is distinct by its colour, petrological composition, grain size and shape, content of organic material - properties that can be unique to a specific spot. The first two samples on the left came from a mountain river with strong current and with granitic rocks in its catchment area, the third from a small, slow flowing creek with basaltic rocks in the surrounding. The fourth comes from a fine-grained soil with a similar bedrock geology like the third sample and the last sample was collected from the entrance of a cave inhabitated by birds (therefore lots of fragments of plants, snails and insects).
Influenced by the rapid development of science, the British author Sir Arthur Conan Doyle introduced in 1887 a new kind of detective, who based his crime solving abilities on the scientific and forensic clues that everybody acquired or left behind by touching objects, or simply walking on muddy ground:
"Knowledge of Geology. - Practical, but limited. Tells at a glance different soils from each other. After walks has shown me splashes upon his trousers, and told me by their colour and consistence in what part of London he had received them."
"Dr. Watson's" description of Holmes's abilities in "A Study in Scarlet"
About at the same time as Holmes fictional adventures, the Austrian professor of criminology Hans Gross (1847-1915) published various textbooks dealing with forensic investigations methods, trying to introduce an ubiquitous standard and comparable investigative approaches.
In his "System der Kriminalistik" (Criminal Investigation, published in 1891), he proposed that the police should carefully study geographical and geomorphological maps, to infer possible sites where criminals could commit crimes or hide bodies - like forests, ponds, streams or sites with a well. In 1893 Gross published his "Handbuch fr Untersuchungsrichter" (Handbook for Examining Magistrates), where he explained how the petrographic composition of dirt found on shoes could indicate where a suspect went previously. Based on these ideas, in 1910 the French physician Edmund Locard (1877-1966) established the basic exchange principle of environmental profiling - when organic or inorganic substances found in the environment connect a suspect with a crime:
"Whenever two objects come into contact, there is always a transfer of material. The methods of detection may not be sensitive enough to demonstrate this, or the decay rate may be so rapid that all evidence of transfer has vanished after a given time. Nonetheless, the transfer has taken place."
The German chemist Georg Popp (1867-1928) was the first investigator to solve a murder case by adopting the principles of Gross and Locard and considering soil as reliable evidence. In the spring of 1908 Margarethe Filbert was murdered near Rockenhausen in Bavaria. The local attorney had read Hans Gross's handbook and know Popp from an earlier case, where Popp connected a strangled woman to the suspect by mineral grains of hornblende found in the mucus of the victim's nose and under the fingernails of the suspect.
In the Filbert case a local factory worker named Andreas Schlicher was suspected, however he claimed that on the day of the murder he was working in the fields.
Popp reconstructed the movements of the suspect by analyzing the dirt found on his shoes. The uppermost layer, thus the oldest, contained goose droppings and earth from the courtyard of the suspect's home. A second layer contained red sandstone fragments and other particles of a soil found also where the body of the victim was discovered. The last layer contained brick fragments, coal dust, cement and a whole series of other materials also found on the site where the suspect's gun and clothing had been found. However, there were no mineral grains - fragments of porphyry, quartz and mica- on the shoes. Since these were found in the soils of the field where Schlicher supposedly worked the very same day, he was obviously lying.
Fig.2. and 3. What if on the shoes of a suspect who claims never to have encountered me during my field trip I found these sediments - the magnified samples could prove that he is lying, and followed me to two localities. The first sample is a grey sediment with lots of large quartz and mica fragments, a very heterogeneous sediment deposited in an instable environment, there are also no organic remains in it. The second sample is composed almost of eroded quartz grains, coated with a thin layer of reddish iron oxides - the lack of other minerals is a result of strong chemical erosion, there are also some organic remains.
Comparing these information with the previously sampled locations - where was the suspect following me ?
In the last two decades, the significance of forensic geology increased steadily. It is applied not only to connect single suspects to criminal cases, but also to trace the provenience of explosive, drugs or smuggled goods, including wildlife, not to mention the possible applications to detect cases against the environmental law. Forensic geology also proved valuable to reconstruct and uncover modern war crimes.
In 1997 the United Nations International Criminal Tribune for the Former Yugoslavia (UN ICTY) began exhuming five mass graves in north-eastern Bosnia associated with the massacre of civilians in and around the town of Srebrenica in July 1995. Intelligence reports showed that 3 months after the initial executions of civilians, the primary mass graves had been exhumed and the bodies transported over a 1-3 day period to a number of unknown (but at least 19) secondary grave sites.
To prosecute the suspects, it was necessary to prove that the now recovered bodies came without doubt from Srebrenica, and that therefore the later dislocation of the graves was intentionally to hide these war crimes. Two grave sites were intensively studied and samples of the grave fills and surrounding soils and bedrock collected. Soil samples can be screened by their content of minerals and rocks, the size and form of single mineral or rock grains, biochemistry of organic substances, microbiology, remains of invertebrates and plants and pollen and spores preserved in it. These various parameters can vary in so many ways, every soil can be regarded as unique. Comparing the parameters between samples recovered from the victim or the suspect and collected at the crime sites it is possible to establish a unique connection between them.
During the investigations in Bosnia a clast of serpentinite found in one of the secondary gravesites proved to be the decisive evidence. This greenish rock connected one secondary grave site with only one primary site - only there an outcrop with a serpentinite dyke could be found. Similarity, the presence or absence of particular clay minerals, depending on the surrounding geology of the primary burial site, connected or excluded the primary to the secondary sites.
These are only some examples of the application of forensic geology. The possible list of fascinating or strange cases would surprise even Sherlock Holmes himself. The only reasonable deduction: whenever a crime is committed, there could and will be a minuscule mineral grain or a pebble that maybe one day will act as testimony against the criminal.
BROWN, A.G. (2006): The use of forensic botany and geology in war crimes investigations in NE Bosnia. Forensic Science International 163: 204-210
PYE, K. (2004): Forensic Geology. In R.C. Selley, L.R.M Cocks and I.R Plimer (ed.) Encyclopedia of Geology. Elsevier: 261- 273
RUFFELL, A. & McKINLEY, J. (2005): Forensic geoscience: applications of geology, geomorphology and geophysics to criminal investigations. Earth-Science Reviews 69: 235-247
RUFFELL, A. & McKINLEY, J. (2008): Geoforensics. John Wiley & Sons: 332
WAGNER, E.J. (2006): The Science of Sherlock Holmes - From Baskerville Hall to the Valley of Fear, the Real Forensics Behind the Great Detective's Greatest Cases. John Wiley & Sons: 244