In 1975, Ray Murray and fellow Rutgers University professor John Tedrow published Forensic Geology.[1]
The main use of forensic geology as it is applied today is regarding trace evidence. By examining the soil and sediment particles forensic geologists can potentially link a suspect to a particular crime or a particular crime scene.
Forensic geologists work with many other disciplines of science such as medicine, biology, geography, and engineering amongst others.[2]
In 2008, Alastair Ruffell and Jennifer McKinley, both of Queen's University Belfast, published Geoforensics[3] a book that focuses more on the use of geomorphology and geophysics for searches. In 2010, forensic soil scientist Lorna Dawson of the James Hutton Institute co-edited and contributed chapters to the textbook Criminal and Environmental Soil Forensics.[4] In 2012, Elisa Bergslien, at SUNY Buffalo State, published a general textbook on the topic, An Introduction to Forensic Geoscience.[5]
Early use of forensic geology
According to Murray, forensic geology began with Sherlock Holmes writer, Sir Arthur Conan Doyle. The character Sherlock Holmes claimed to be able to identify where an individual had been by various methods, including his having memorized the exposed geology of London to such a degree that detecting certain clays on a person's shoe would give away a locale. Georg Popp, of Frankfurt, Germany, may have been the first to use soil analysis for linking suspects to a crime scene.[6] In 1891, Hans Gross used microscopic analysis of soils and other materials from a suspect's shoes to link him to the crime scene.[7]
Physical description
Colour
Displaying Munsell Book of colour.
Colour is one of the most important physical characteristics associated with soil samples. One technique used is comparing the soil to the Munsell soil chart. In a majority parts of the world during a forensic investigation determining the soil colour is required. This analysis can be achieved in the field itself with the Munsell soil chart using human perspective. Although colour is a very subjective topic, two people can have a complete different perception of colour and could then associate it differently with the Munsell soil chart thus effecting the accuracy of this method.[2]
.To avoid the errors of simply using human perception, to obtain objective results computer controlled spectrophotometry can be used. One computerized method is using CIELAB which consists of using an electronic spectrophotometer and calorimeter to create 3D plotting of colour. Using three coordinates L* relates to a reflection of lightness, a* refers to red/ green colours and b* yellow/ blue colours. This method uses a derivative mathematical system to achieve a uniform colour space for analysis. This technique provides numerical values to be associated with colour to then be using with accordance of the Munsell soil chart.[8]
The most commonly used technique to determine colour of a soil sample has been measuring the colour once the sample has been dried. Although to obtain a more thorough analysis different case studies have taken colour measurements when the soil sample is moist, allowing organic materials to decompose, removing iron oxides, crushing and heating the sample.[9]
Density
Another physical characteristic used is measuring the density in units of or . This can be achieved in regards to the particle density or material density, this measurement will vary depending on the specific type of material measured. To determine the weight of the sample in question a simple scale is used. To determine the volume of the sample, if it is a rock being measured, it can be placed in water and be measured by the displacement. In regards to soil sample the same technique is used although the soil sample is placed in a cling film to avoid disintegration. The main use of density of the sample in forensic geology is to obtain the best description of the sample in question.[2]
Particle size distributions
One of the most discriminating physical characteristics consist of particle size where it is characterized as particle size frequency distributions. This consists of the materials weight, weight%, number of particles present, or the volume. Depending on the sample, different methods can be used such as examination use a microscope, laser diffraction, dry/ wet sieving, computer program analysis and many more.[2]
Chemical description
Ph
Ph is the measure of hydrogen activity present and to determine the pH they calculate the level of dissociation of the hydrogen ions. Within the realm of pH it can be associated with acidic, basic or neutral. Although more can be determined with pH such as the elemental composition and the level of essential nutrients and toxicity. It can indicate the presence of many elements such as P, Zn, B, Cu, Fe etc., as well as estimating lime requirement.
In recent years that has been much improvement to portable pH meters that are used in the field. Decades ago the portable devices has numerous malfunctions regarding the electrodes. Nowadays pH meters due to microcircuitry and plastic not only reduces the cost of these devices but also allows for an overall better protection of the unit. Further studies are attempting a technique to produce a device to obtain microsite pH in various soil systems by using plant cells via microprocedures. This would also be able to decipher the different pH present in the soil matrix. [10]
Evidence collection
In the application of forensic geology there are two distinct types of soil samples. The first being the questioned sample, samples of unknown origin. These types of sample can be taken from someones shoe for example. The other type of sample consists of the control sample which the forensic geologist can choose. The most common control sample would be soil taken from the crime scene. The questioned and control sample would then be compared to find similarities or distinction from the two.[11]
Regarding the evidence collection from a questioned sample, these are most likely samples acquired by accident. Such as a suspect obtained soil or rocks in their shoes or pants. The forensic geologist therefor does not chose the size of the questioned sample and most likely will not be comparable in size to the control sample. Depending on the question sample the forensic geologist will have to use professional judgement on the optimal technique to compare it to the control sample. In some situations only loose particles are available for comparison. If the questioned sample is found to be a lump of soil, this lump needs to obtained in its entirety to essentially preserve the different layers of soil in the lump itself as well as the keeping intact the particles. Methods such as using adhesive tape, vacuuming, shaking items over a tarp are also used in the field.[12]
Controlled samples consist of two sub categories samples from the scene itself or an alibi location. Soil samples can differ from a very small distance and is why the questioned sample should be examined first two establish particle size/ colour or any other distinguishable factors to then carefully choose a location at the scene to sample in comparison. Samples obtained from these scenes can also be submitted to the forensic lab with other physical evidence. Depending on the lab, they would have distinct instructions for the collector on how the sample is collected/ submitted. When samples are being taken from the ground it is recommended to take samples from different layers of the soil such as the horizon or the bed layer. It is important to obtain samples that vary on colour, mineral composition and textures.[12]
The tools used to collect evidence depend on type of sample either questioned or control as well as its structure and size. Smaller quantities of soil can bee retrieved using forceps, tweezers, palette knives etc. When attempting to remove soil that is stuck to a surface an ice pick, razor blade or anything with a flat surface is sufficient. Control samples are normally larger thus requiring the implementation of a larger tool such as a garden shovel.[11] When taking a soil sample from the ground normally just the surface is being sampled. Need to assure the samples are allowed to dry before collection, moist samples will still allow further biological material will be modified changing the overall composition of the sample. Dry samples can be placed in plastic cartons/ vials and leak proof containers. To avoid continuous microbial activity related to sample taken from damp area, they are refrigerated prior.[12]
Geophysical Instruments
Ground penetrating radar
The principle use of a ground-penetrating radar device in regards to forensic geology is to find buried bodies. This instrument has been most useful in resolving missing person cases. As well improving the recovery of the body by giving a general area to which the body is buried this also decreases excavation time. Studies conducted using this device show data of its capability to discover hallow and forensic relevant locations as well as specific geometries.[13] This method includes reflective signalling off of objects in the ground that undergo different electronic properties via a transmittance signal. The actual device contains a radio transmitter and receiver that attaches to antennas that are attached to the ground.[12]
Seismograph
Seismograph produced from the 1906 San Francisco earthquake
The seismograph devices functions under the principle of waves that travel differently through rocks and are recorded as vibrations. For it to function properly there must be shocks produced and a manor on detecting these waves. Depending on the rocks under the earth, the waves will travel at different velocities. This is measured through the time it takes for waves to reach the area of shock along with the time it takes to reach the detector.[12] In forensic applications, the device is used to understand explosives and differentiating them from natural occurrences such as earthquakes. Because of the varying surface wave magnitude varies significantly between both occurrences. Natural disasters emit longer and higher intensity energy then man mad events such as chemical explosions, nuclear explosion, plane or train crashes.[14]
↑ Murray, Raymond C. and Tedrow, John C. F. (1975) Forensic Geology: Earth sciences and criminal investigation Rutgers University Press, New Brunswick, New Jersey, ISBN978-0-8135-0794-1; second edition 1992, Prentice Hall, Englewood Cliffs, New Jersey, ISBN978-0-13-327453-0; replaced by Murray, Raymond C. (2004) Evidence from the Earth: Forensic geology and criminal investigation Mountain Press Publications, Missoula, Montana, ISBN978-0-87842-498-6
↑ Bell, Suzanne (2004) "geology, forensic" The Facts on File Dictionary of Forensic Science Infobase Publishing, New York, page 102, ISBN978-0-8160-5153-3
Geotechnical engineering, also known as geotechnics, is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics to solve its engineering problems. It also relies on knowledge of geology, hydrology, geophysics, and other related sciences.
Neutron activation analysis (NAA) is a nuclear process used for determining the concentrations of elements in many materials. NAA allows discrete sampling of elements as it disregards the chemical form of a sample, and focuses solely on atomic nuclei. The method is based on neutron activation and thus requires a neutron source. The sample is bombarded with neutrons, causing its constituent elements to form radioactive isotopes. The radioactive emissions and radioactive decay paths for each element have long been studied and determined. Using this information, it is possible to study spectra of the emissions of the radioactive sample, and determine the concentrations of the various elements within it. A particular advantage of this technique is that it does not destroy the sample, and thus has been used for the analysis of works of art and historical artifacts. NAA can also be used to determine the activity of a radioactive sample.
Forensic science, also known as criminalistics, is the application of science principles and methods to support legal decision-making in matters of criminal and civil law.
Forensic palynology is a subdiscipline of palynology, that aims to prove or disprove a relationship among objects, people, and places that may pertain to both criminal and civil cases. Pollen can reveal where a person or object has been, because regions of the world, countries, and even different parts of a single garden will have a distinctive pollen assemblage. Pollen evidence can also reveal the season in which a particular object picked up the pollen. Recent research into forensic palynology has seen advancements in DNA barcoding from pollen, to the level of singular pollen molecules, allowing DNA profiles to be created from singular palynomorphs, streamlining the efficiency and accuracy of taxonomic identification.
Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in sediments, sedimentary rocks, and even some metasedimentary rocks. Palynomorphs are the microscopic, acid-resistant organic remains and debris produced by a wide variety plants, animals, and Protista that have existed since the late Proterozoic.
Geoarchaeology is a multi-disciplinary approach which uses the techniques and subject matter of geography, geology, geophysics and other Earth sciences to examine topics which inform archaeological knowledge and thought. Geoarchaeologists study the natural physical processes that affect archaeological sites such as geomorphology, the formation of sites through geological processes and the effects on buried sites and artifacts post-deposition. Geoarchaeologists' work frequently involves studying soil and sediments as well as other geographical concepts to contribute an archaeological study. Geoarchaeologists may also use computer cartography, geographic information systems (GIS) and digital elevation models (DEM) in combination with disciplines from human and social sciences and earth sciences. Geoarchaeology is important to society because it informs archaeologists about the geomorphology of the soil, sediment, and rocks on the buried sites and artifacts they are researching. By doing this, scientists are able to locate ancient cities and artifacts and estimate by the quality of soil how "prehistoric" they really are. Geoarchaeology is considered a sub-field of environmental archaeology because soil can be altered by human behavior, which archaeologists are then able to study and reconstruct past landscapes and conditions.
Trace evidence occurs when objects make contact, and material is transferred. This type of evidence is usually not visible to the naked eye and requires specific tools and techniques to be located and obtained. Due to this, trace evidence is often overlooked, and investigators must be trained to detect it. When it comes to an investigation trace evidence can come in many different forms and is found in a wide variety of cases. This evidence can link a victim to suspects and a victim or suspect to the crime scene.
Forensic identification is the application of forensic science, or "forensics", and technology to identify specific objects from the trace evidence they leave, often at a crime scene or the scene of an accident. Forensic means "for the courts".
A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The hole made for the core sample is called the "core hole". A variety of core samplers exist to sample different media under different conditions; there is continuing development in the technology. In the coring process, the sample is pushed more or less intact into the tube. Removed from the tube in the laboratory, it is inspected and analyzed by different techniques and equipment depending on the type of data desired.
Soil texture is a classification instrument used both in the field and laboratory to determine soil classes based on their physical texture. Soil texture can be determined using qualitative methods such as texture by feel, and quantitative methods such as the hydrometer method based on Stokes' law. Soil texture has agricultural applications such as determining crop suitability and to predict the response of the soil to environmental and management conditions such as drought or calcium (lime) requirements. Soil texture focuses on the particles that are less than two millimeters in diameter which include sand, silt, and clay. The USDA soil taxonomy and WRB soil classification systems use 12 textural classes whereas the UK-ADAS system uses 11. These classifications are based on the percentages of sand, silt, and clay in the soil.
Fingerprint powders are fine powders used, in conjunction with fingerprint brushes, by crime scene investigators and other law enforcement personnel to search for and enhance latent/invisible fingerprints that can be used to determine identification. This method of fingerprint development commonly referred to as dusting for fingerprints, involves the adherence of the powder particles to the moisture and sweat secretions deposited on to surfaces by the raised ridges on fingers, palms, or soles of feet designed for grip, called friction ridges. Furrows, representing the recessed areas, which lack fingerprint residue, do not retain the powder.
Forensic biology involves the application of biological principles and techniques within the context of law enforcement investigations.
Forensic photography may refer to the visual documentation of different aspects that can be found at a crime scene. It may include the documentation of the crime scene, or physical evidence that is either found at a crime scene or already processed in a laboratory. Forensic photography differs from other variations of photography because crime scene photographers usually have a very specific purpose for capturing each image. As a result, the quality of forensic documentation may determine the result of an investigation; in the absence of good documentation, investigators may find it impossible to conclude what did or did not happen.
The following outline is provided as an overview of and topical guide to forensic science:
Forensic materials engineering, a branch of forensic engineering, focuses on the material evidence from crime or accident scenes, seeking defects in those materials which might explain why an accident occurred, or the source of a specific material to identify a criminal. Many analytical methods used for material identification may be used in investigations, the exact set being determined by the nature of the material in question, be it metal, glass, ceramic, polymer or composite. An important aspect is the analysis of trace evidence such as skid marks on exposed surfaces, where contact between dissimilar materials leaves material traces of one left on the other. Provided the traces can be analysed successfully, then an accident or crime can often be reconstructed. Another aim will be to determine the cause of a broken component using the technique of fractography.
Particle size analysis, particle size measurement, or simply particle sizing, is the collective name of the technical procedures, or laboratory techniques which determines the size range, and/or the average, or mean size of the particles in a powder or liquid sample.
Nuclear forensics is the investigation of nuclear materials to find evidence for the source, the trafficking, and the enrichment of the material. The material can be recovered from various sources including dust from the vicinity of a nuclear facility, or from the radioactive debris following a nuclear explosion.
Forensic firearm examination is the forensic process of examining the characteristics of firearms or bullets left behind at a crime scene. Specialists in this field try to link bullets to weapons and weapons to individuals. They can raise and record obliterated serial numbers in an attempt to find the registered owner of a weapon and look for fingerprints on a weapon and cartridges.
Forensic colorimetry, or forensic color analysis, is the examination of specimen color for purposes of forensic investigation. Typical specimens involved in color analyses include pigments, dyes, or other objects that are distinguishable by their intrinsic color. Analyses may be conducted by-eye or by computational methods, both by matching specimen colors to a standardised chart or database.
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