This note provides basic knowledge on forensic geology and forensic science, which is an application of science that contributes to solving crimes. Forensic geology is part of forensic sciences, which applies knowledge of geology and its associated sciences to forensic investigation. The history of forensic geology exceeds 100 years in Europe, and it was introduced in Japan soon after World War II. Forensic geology comprises three categories: ground search for burial sites, crime scene investigation, and examination of geological trace evidence. The majority of geological trace evidence comes from soil samples. Discrimination between soil evidence adhered to items and control samples from the crime scene is performed using observations and subsequent analyses. Law enforcement processes often require smaller quantities and well-established, rapid, non-destructive analysis methods for forensic samples, which differ from traditional geologic investigations. With the recent introduction of the lay judge system in Japan, people may have increasing opportunities to see geological evidence presented in court. Unfortunately, there are few forensic geologists in Japan, and thus there are limited opportunities to learn forensic science. Increasing education opportunities at universities and high schools, and promoting forensic geology at academic meetings are essential to advances in forensic geology.

Soil can provide important information as forensic trace evidence in criminal investigations, and various analyses, mainly based on geologic methods, are applied to discriminate between soil evidence and control samples. To improve the discriminating power of soil, it is necessary to investigate new analyses based on other characters. Quartz grains in soil are highly resistant to weathering and preserve various surface microtextures that reflect the sedimentary history of the grains. The microtextures of quartz are observed using scanning electron microscopy (SEM). Previous research has demonstrated the utility of quartz surface analyses in forensic examinations. However, quartz microtextures observed in soil from Japan may differ from those reported in previous foreign studies owing to their different geological history and geomorphological setting. To apply quartz analysis to forensic examination in Japan, we first need to survey the morphological diversity of quartz grains from Japan. To this end, we collected 38 sediment samples from rivers and beaches of Japan. Fifteen types of microtextures on the quartz surfaces were identified using SEM and the data were statistically processed. The quartz shapes were evaluated in terms of roundness and fractal dimension using image analysis. Roundness and fractal dimension were correlated and provide a quantitative measure of grain angularity. Samples from similar depositional environments were grouped by principal component analysis (PCA), and the surface textures and shapes of quartz showed diversity across the study areas. Image analysis, SEM observations, and PCA showed good repeatability and therefore may be applied in forensic discrimination. Most types of surface microtextures reported by previous foreign studies were also observed in Japan, but some types were rarely observed compared with previous studies. Therefore, forensic investigations involving quartz analysis need to assess grain provenance with reference to the geological and geomorphological history of grains from Japan.

This paper is a review of the history of forensic geology and related disciplines in Japan. In crime investigations, soil is an important piece of evidence that may demonstrate relationships between persons, tools, and locations. In Japan, discrimination analysis is typically implemented when comparing the soil in question to a reference soil. As the needs for soil examination increased, a systematic method of soil examination and related materials was proposed in 1950. This method involvedchemical and physical observations, which include density gradient distribution, grain size distribution, microscopy, pH measurement, and chemical component analysis. Soil examination procedures were further developed during the 1970s-1990s, and involve pretreatment procedures (sieving, organic decomposition, and iron removal) followed by microscopy and instrumental analyses (X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectrometry). Recently, interest in forensic geology has increased in some academic societies; thus, we expect future collaborations between practical investigations and research and educational institutions.

The development of forensic geology has been remarkable throughout the twenty-first century, although the demands and roles of forensic geology differ from nation to nation. This review describes recent global developments in forensic geology, with a focus on soil as trace evidence. Existing reviews of forensic geology have been published in English language books and academic journals, which are less familiar to the readers of the Journal of the Geological Society of Japan. This paper is written as an introduction to the global status of this field, and refers to previously published reviews and adds new information. It includes the establishment of an international network, academic meetings, publication trends, education and practice, overviews of situations around the world, and note-worthy study areas and case reports for soil as forensic evidence.

The Geoforensic Search Strategy (GSS) is a model to apply in searches to locate burials including homicide graves, terrorist and criminal hides. The objective of this paper is to introduce the GSS to forensic geologists, police and law enforcement in Japan. The GSS has been developed and refined over a period of approximately 25 years and brings together mineral exploration, engineering geology, ground investigative techniques and conventional law enforcement search techniques. This blended approach provides for the first time high assurance methodologies in searches for burials. The GSS is divided into three main phases. In the pre-search phase, the search type is determined and the role of the forensic geologist in supporting law enforcement is defined. The pre-search phase is based on the production of a conceptual geological model (CGM), based on available geological data and information, police intelligence and supplemented by a reconnaissance walk-over survey of the search area. CGM provides the basis for the evaluation of ground diggability and detectability and helps determine the suite of search assets likely to locate the burial (e.g. geophysics and detector dogs). The search phase represents the actual deployment of the search in accordance with an agreed standard operating procedure (SOP). This commences with the establishment of geophysical and detector dog controls to verify whether the search assets are fit-for purpose. This also enables geophysical equipment calibration and, if required, the training of law enforcement search trained officers to become familiarised with the search assets. The post search phase focuses on the forensic recovery and recording of any items found. Finally, a briefing with the search team takes place and a pre-determined exit strategy. The GSS provides a framework that can be adapted or adopted to suite the particular set of circumstances unique to each ground search.

Forensic geology makes use of analyses of mineral, rock fragment, soil, sediment, and suspended solid samples collected from incident, accident, and crime scenes as evidence. This paper discusses magnetic measurements as an analytical tool for analyzing evidence. Compared with traditional chemical methods, magnetic measurements are a quick, non-destructive, and effective tool that can detect grain size, quantity, and types of magnetic minerals in evidence and control samples. Magnetic measurements for forensic geology are an applied technique based on methods from rock magnetism, environmental magnetism, and archaeological magnetism. Here, we report magnetic data from disturbed and burned soils, and discuss load sediments and how to detect the origins of suspended solids. To develop applications for magnetic measurements in forensic geology, it is important to elucidate the alteration rate of magnetic minerals by rainfall in soil in Japan. The construction of a soil database that covers a large area, and the use new measurement techniques, which can detect very weak magnetization in soil and sediment samples, are needed to fully develop magnetic measurements as a robust tool for forensic geology.