Forensic geoscience

DEFINITION: Scientific field that applies geological information and earth science techniques to investigations related to criminal or other legal proceedings.

SIGNIFICANCE: An almost unlimited variety of earth materials, minerals, rocks, and fossils can be identified, characterized, and recognized for comparative analysis. Given the diversity of composition and unique distribution of earth materials, forensic geoscience is a useful tool for linking suspects to crime scenes.

Forensic geoscience first appeared in Sir Arthur Conan Doyle’s tales of the fictional detective Sherlock Holmes, who used scientific to solve crimes. The first real use of forensic geoscience occurred during a 1908 case in Germany, where Georg Popp, a chemist, examined soil and rock samples from a scene and compared them with samples from a suspect’s shoes. Popp’s analysis of the samples was able to disprove the suspect’s alibi. Forensic geoscience techniques are usually used in lawsuit litigation between plaintiff and or in processing to provide evidence leading to the or exoneration of criminal suspects.

Basis of Forensic Geoscience

Forensic geoscience is concerned with all aspects of earth materials and natural processes and phenomena associated with them, including investigations of rocks, sediments, water, air, soil, gems, fossils, dust, pollutants, and petroleum. Because of the breadth of its investigative concerns, forensic geoscience relies on many subdisciplines to accomplish its investigative goals. A forensic geoscience investigation may require the expertise of hydrologists, geophysicists, mineralogists, geoarchaeologists, gemologists, pedologists, petroleum geologists, stratigraphers, geochemists, paleontologists, geoengineers, or petrologists.

The fundamental principle in all forensic geoscience investigations is transference. Whenever any object comes into contact with another, is transferred between the two objects. Geological materials and markers, whether natural or combined with other products, provide an abundance of transferable signatures. In the case of geological trace evidence, the transferred evidence often has unique characteristics that can be recognized and categorized. Identifying the signature of the trace evidence preserved from the transfer is crucial to identifying the source of the evidence. Because the value of earth materials as evidence is in their diversity and, often, their unique compositions, identifying the differences between samples is crucial.

Investigative Techniques

Some of the most important aspects of any are the questions of whether a was present during the commission of a crime and whether evidence can be directly linked to a suspect or specific crime scene. Investigators often provide forensic geoscientists with samples associated with crime scenes or suspects, and the two things investigators most commonly want to know about such samples are where the materials came from and whether the materials can be linked to the crime.

The first step the forensic geoscientist takes in establishing the unique composition of earth materials from a crime scene is usually visual inspection; this is followed by geochemical tests. After studying the samples, identifying, and classifying them, the geoscientist can usually narrow down possible sources of the material. The accuracy of the conclusions drawn depends on the uniqueness of the sample materials and the knowledge and experience of the geoscientist. It is often during the initial stage of sample testing by geoscientists that additional forensic evidence is found, including fibers, hairs, insects, and botanical trace evidence such as pollens, seeds, and cellulose. These additional pieces of evidence not only aid in the overall investigation but can also help the forensic geoscientist to narrow the sample’s source parameters.

Forensic geoscientists use specialized techniques and are aided by equipment designed to detect small variations in the structure and chemical composition of earth materials. The purpose of detecting these small variations is to establish with the highest possible degree of probability whether a sample is similar to other samples from a specific geographic location. In the initial stages of examining a sample, a geoscientist measures the material’s particle density distribution, notes its color and size, determines its mineral composition, and looks for biological, botanical, and fossil additions.

The most fundamental technique used by forensic geoscientists is chemical analysis for characteristic trace elements. These trace elements are derived from, and usually particular to, their original bedrock source, or they can be associated to a specific contaminated locality. Geoscientists use many techniques to confine sample variations and narrow the degree of probability in samples under investigation, including examination using specialized optical and electron microscopes, X-ray and laser diffraction, spectroscopy, gas chromatography, and chemical, fluorescence, and isotopic analyses.

Bibliography

Fitzpatrick, Robert W., and Laurance J. Donnelly. “An Introduction to Forensic Soil Science and Forensic Geology: A Synthesis.” Lyell Collection, 19 July 2021, www.lyellcollection.org/doi/full/10.1144/SP492-2021-81. Accessed 14 Aug. 2024.

Murray, Raymond C. Evidence from the Earth: Forensic Geology and Criminal Investigation. Missoula, Mont.: Mountain Press, 2005. One of the most easily understood and directly useful books available on the subject of forensic geology. Discusses numerous criminal cases involving forensic geology.

Murray, Raymond C., and John C. F. Tedrow. Forensic Geology: Earth Science and Criminal Investigation. Upper Saddle River, N.J.: Prentice Hall, 1998. Comprehensive work is an update of the classic text on forensic geology.

Pye, Kenneth. Geological and Soil Evidence: Forensic Applications. Boca Raton, Fla.: CRC Press, 2007. Helpful reference resource provides guidance regarding the potential value and limitations of geological and soil evidence in forensic investigations.

Pye, Kenneth, and D. J. Croft, eds. Forensic Geoscience: Principles, Techniques, and Applications. London: Geological Society, 2004. Collection of papers illustrates the principles of forensic geoscience and provides in-depth discussion of the techniques used in the field.

Selinus, Olle, et al., eds. Essentials of Medical Geology: Impacts of the Natural Environment on Public Health. Burlington, Mass.: Elsevier, 2005. Addresses the intersection of environmental geosciences and human health, with special emphasis on toxic mineral contamination of land and water.

Wang, Zhendi, and Scott A. Stout. Oil Spill Environmental Forensics: Fingerprinting and Source Identification. Burlington, Mass.: Elsevier, 2007. Describes the forensic techniques used by geoscientists to identify the sources of oil spills. Case studies include the Exxon Valdez incident of 1989.