Field of Science

It’s sedimentary, my dear Watson

February 20, 1949 Mrs. Henrietta Helen Olivia Roberts Durand-Deacon, a wealthy widow, disappeared from the Onslow Court Hotel located in South Kensington, London. The police interviewed the residents and soon John George Haigh became a suspect, as he was the last person to have be seen together with the woman. 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.

During the 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. 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.“ 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. A thin layer of organic matter 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 later to death.

This forensic case was an unusual example of how rocks 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.

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."

About at the same time as Doyle published his fictional adventures, the Austrian professor of criminology Hans Gross (1847-1915) published various textbooks dealing with forensic investigations methods. In his “System der Kriminalistik” (Criminal Investigation, published in 1891) he proposed that the police should carefully study 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 für 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:
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.

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.

The list of fascinating or strange cases solved thanks to forensic geology would surprise even Sherlock Holmes himself.

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