4,994 research outputs found
Normative decision analysis in forensic science
No full textThis paper focuses on the normative analysis – in the sense of the classic decision-theoretic formulation – of decision problems that arise in con- nection with forensic expert reporting. We distinguish this analytical account from other common types of decision analyses, such as descriptive approaches. While decision theory is, since several decades, an extensively discussed topic in legal literature, its use in forensic science is more recent, and with an em- phasis on goals such as the analysis of the logical structure of forensic ex- pert conclusions regarding, for example, propositions of common source of evidential and known materials. Typical examples are so-called identification (or, individualization) decisions, especially categorical conclusions according to which fingermarks (or stains of biological nature, handwriting, etc.) come from a particular a person of interest. We will present and compare ways of stating forensic identification decisions in decision-theoretic terms and explain their underlying rationale. In particular, we will emphasize the importance of viewing this analysis as normative in the sense of providing a reflective rather than a prescriptive reference point against which people in charge of forensic identification decisions may compare their otherwise (possibly) intuitive and informal reasoning, before acting. Normative decision analysis in forensic sci- ence thus provides a vector through which current practice can be articulated, scrutinized and rethought
Evaluation and reporting of scientific evidence: the impact of partial probability assignments
No full textThe assessment of the value of scientific evidence can be performed by the derivation of a likelihood ratio, a rigorous concept that provides a measure of the change produced by an item of information in the odds in favor of a proposition as opposed to another. This represents a demanding task with several sources of uncer- tainty, due for example to elicitation of probabilities or to computational impasses. While use of such a metric is well established and supported by operational stan- dards, opinions about what should be an appropriate way to deal with such sources of uncertainty while presenting expressions of evidential value at trial differ. Some quarters promote positions according to which practitioners should state a range of values for the probabilities of the evidence given competing propositions, and report a range of values for the likelihood ratio. However, such partial probability assignments may not make good use of available information
A probabilistic graphical model for assessing equivocal evidence
No full textThe Bayes' theorem can be generalized to account for uncertainty on reported evidence. This has an impact on the value of the evidence, making the computation of the Bayes factor more demanding, as discussed by . Probabilistic graphical models can however represent a suitable tool to assist the scientist in their evaluative task. A Bayesian network is proposed to deal with equivocal evidence and its use is illustrated through examples
A system for dimensional analysis of mechanical objects by means of optical filtering
No full textNon-contact electrooptical techniques offer the possibility of using automatic measurement for on-line dimensional analysis and quality control. In this paper a simple method, based on optical image elaboration using filtering techniques in the Fourier plane, is presented. The method enhances the signal-to-background ratio and can eliminate undesired spatial components in the image light distribution. The result of pre-filtering is a quasi- digital presentation of the object profile that reaches the CCD camera directly. A preliminary implementation of the system is described, both for one- and two-dimensional ob- jects, and significant experimental results are presented
Contaminazioni di un reperto con il DNA. Quando la prova genetica porta direttamente alla condanna.
No full textA generalised Bayes' factor formula for evidence evaluation under activity level propositions: variations around a fibres scenario
No full textGeneralised Bayes' factors and associated Bayesian networks are developedfor the transfer of extrinsic evidence at the activity level, developments thatextend previous work on activity level evaluation. A strategy for the assessmentof extrinsic evidence is developed in stages with progressive increases incomplexity. The final development is illustrated with an example involvingfibres from clothing. This provides a list of factors involved in the considerationof a transfer case with activity level propositions and their roles in thedetermination of evidential valu
Coherently updating degrees of belief: Radical probabilism, the generalization of Bayes’ Theorem and its consequences on evidence evaluation
No full textThe Bayesian perspective is based on conditioning related to reported evidence that is considered to be certain. What is called ‘Radical Probabilism’ replaces such an extreme view by introducing uncertainty on the reported evidence. How can such equivocal evidence be used in further infer- ences about a main hypothesis? The theoretical ground is introduced with the aim of offering to the readership an explanation for the generalization of the Bayes’ Theorem. This extension—that con- siders uncertainty related to the reporting of evidence—also has an impact on the assessment of the value of evidence through the Bayes’ factor. A generalization for such a logical measure of the evidence is also presented and justified
Evidence, probability and relative plausibility
No full textA comparison is made between probability and relative plausibility as approaches for the interpretation of evidence. It is argued that a probabilistic approach is capable of answering the criticisms of the proponents of relative plausibility. It is also shown that a probabilistic approach can answer the problem of overlapping where there is evidence that each side claims supports its theory of what happened
After Uniqueness: The Evolution of Forensic Science Opinion
No full textBig changes are occurring in forensic science, particularly among experts who compare the patterns found in fingerprints, footwear impressions, toolmarks, handwriting, and the like. Forensic examiners are reaching conclusions in new ways and changing the language they use in reports and testimony. This article explains these changes and the challenges they pose for lawyers and judges.This is an article published as Thompson, William C., Joelle Vuille, Franco Taroni, and Alex Bidermann. "After uniqueness: the evolution of forensic science opinions." Judicature 102 (2018): 18. Posted with permission of CSAFE.</p
Dismissal of the illusion of uncertainty in the assessment of a likelihood ratio
No full textThe use of the Bayes factor (BF) or likelihood ratio as a metric to assess the probative value of forensic traces is largely supported by operational standards and recommendations in different forensic disciplines. However, the progress towards more widespread consensus about foundational principles is still fragile as it raises new problems about which views differ. It is not uncommon e.g. to encounter scientists who feel the need to compute the probability distribution of a given expression of evidential value (i.e. a BF), or to place intervals or significance probabilities on such a quantity. The article here presents arguments to show that such views involve a misconception of principles and abuse of language. The conclusion of the discussion is that, in a given case at hand, forensic scientists ought to offer to a court of justice a given single value for the BF, rather than an expression based on a distribution over a range of values
- …
