The forensic sciences are under review more so than ever before. Such review is necessary and healthy and should be a continuous process. It identifies areas for improvement in quality practices and services. The issues surrounding error, i.e., measurement error, human error, contextual bias, and confirmatory bias, and interpretation are discussed. Infrastructure is already in place to support reliability. However, more definition and clarity of terms and interpretation would facilitate communication and understanding. Material improvement across the disciplines should be sought through national programs in education and training, focused on science, the scientific method, statistics, and ethics. To provide direction for advancing the forensic sciences a list of recommendations ranging from further documentation to new research and validation to education and to accreditation is provided for consideration. The list is a starting point for discussion that could foster further thought and input in developing an overarching strategic plan for enhancing the forensic sciences.
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Soil and geologic evidence has been examined in the FBI Laboratory since 1939, and long admitted into trials, both in the US and abroad. However, to the best our knowledge soil evidence did not undergo a formal admissibility challenge within the US court systems until 29 th January 2016. Forensic soil analysis is typically a comparison between two or more samples to see whether they originated from different sources. When soil samples are indistinguishable, the possibility that they originated from a single source cannot be eliminated. The challenge in State of Kansas v. Kyle Flack, 13CR104 (2016), involved the admissibility of soil comparisons at the trial, as well as the qualifications of the forensic geologist who conducted the examinations. The views expressed are those of the authors and do not necessarily reflect the official policy or position of the FBI. Names of commercial manufacturers are provided for identification purposes only, and inclusion does not imply endorsement of the manufacturer or its products or services by the FBI.
Examinations of soil traces associated with forensic evidence can be used to narrow potential source area(s) by characterizing features of the trace soil assemblage, some of which are limited to specific regions. Soil characteristics may be used to infer the likelihoods of the soil trace being derived from distinct areas within digital maps, including both maps of discrete classes such as formations on geologic maps and land cover, and continuous geospatial data, such as distance from a point source. Seldom do digital maps precisely represent the observable characteristics in a soil trace. Nevertheless, logical assigned likelihoods based on the correspondence between the mapped characteristics and the observed soil particulate assemblage permit creation of a model of the more probable sources of the soil trace. This approach is applied to a 2003 case in which forensic soil samples derived from digging tools were characterized for investigative leads and to narrow the search area of a clandestine grave. This grave site was located in 2005. The suspect traveled approximately 5,000 km before arrest, so narrowing the prioritized search area for law enforcement would be beneficial. Soil examination and case circumstances were used to assign relative likelihoods within digital maps (GIS or Geographic Information Systems data) of geology, soil mineralogy, plant distributions, power plant locations, and proximity to the known travel path. The product of these individual probability maps generates joint probability models to narrow the recommended search area. The digital model output can be easily overlaid on infrastructure maps to aid law enforcement searches.
Forensic Interpretation of Glass Evidence begins with a brief overview of the physical properties of glass, methods for glass analysis, classical approaches to the interpretation of forensic glass data, and glass transfer and persistence studies. Building on this foundation, the Bayesian method of interpretation is outlined, and the authors discuss some of the various parameters that may be necessary for a Bayesian analysis. The Bayesian method is a statistical treatment that uses a “continuous approach” to evidence interpretation that abandons the conventional “match/non-match” treatment of the data. The Bayesian method, as presented in this book, uses the likelihood ratio to numerically represent the weight of the evidence. The likelihood ratio is an expression for the relative probabilities of the evidence under competing hypotheses. The significance of a measured parameter, limited in the text to refractive index (RI), is modified by taking into account factors such as the background information (eyewitness statements, previous criminal activity, . . .), presence, transfer, and persistence of glass.
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