1,721,051 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
A formal approach to qualifying and quantifying the ‘goodness’ of forensic identification decisions
Full text linkIn this article, we review and analyse common understandings of the degree to which forensic inference of source—also called identification or individualization—can be approached with statistics and is referred to, increasingly often, as a decision. We also consider this topic from the strongly empirical perspective of PCAST (2016) in its recent review of forensic science practice. We will point out why and how these views of forensic identification as a decision, and empirical approaches to it (namely experiments by multiple experts under controlled conditions), provide only descriptive measures of expert performance and of general scientific validity regarding particular forensic branches (e.g. fin- germark examination). Although relevant to help assess whether the identification practice of a given forensic field can be trusted, these empirical accounts do not address the separate question of what ought to be a sensible, or ‘good’ in some sense, (identification-)decision to make in a particular case. The latter question, as we will argue, requires additional considerations, such as decision-making goals. We will point out that a formal approach to qualifying and quantifying the relative merit of competing forensic decisions can be considered within an extended view of statistics in which data analysis and inference are a necessary but not sufficient preliminary
La naturaleza decisoria de las conditionnes de los expertos en ciencia forense
No full textThroughout forensic science and adjacent branches, academic researchers and practitioners continue to di- verge in their perception and understanding of the notion of ‘individualization’, that is the claim to reduce a pool of potential donors of a forensic trace to a single source. In particular, recent shifts to refer to the practi- ce of individualization as a decision have been revealed as being a mere change of label (Cole, 2014), leaving fundamental changes in thought and understanding still pending. What is more, professional associations and practitioners shy away from embracing the notion of decision in terms of the formal theory of decision i ic iiialiatio a b ra ail bca o iclti to al it t art o desirability or undesirability of the consequences of decisions (e.g., using utility functions). Building on exis- ting research in the area, this paper presents and discusses fundamental concepts of utilities and losses with particular reference to their application to forensic individualization. The paper emphasizes that a proper appreciation of decision tools not only reduces the number of individual assignments that the application of decision theory requires, but also shows how such assignments can be meaningfully related to constituting features of the real-world decision problem to which the theory is applied. It is argued that the decisona- lization of individualization rir c atal iigt to iitiat cag i t fil rlig understandings, not merely in their label
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
The meaning of justified subjectivism and its role in the reconciliation of recent disagreements over forensic probabilism
Full text linkIn this paper we reply to recent comments in this Special Issue according to which subjective probability is not considered to be a concept fit for use in forensic evaluation and expert reporting. We identify the source of these criticisms to lie in a misunderstanding of subjective probability as unconstrained subjective probability; a lack of constraint that neither corresponds to the way in which we referred to subjective probability in our previous contributions, nor to the way in which probability assignment is understood by current evaluative guidelines (e.g., of ENFSI). Specifically, we explain that we understand subjective probability as a justified assertion, i.e. a conditional assessment based on task-relevant data and information, that may be thought of as a constrained subjective probability. This leads us to emphasise again the general conclusion that there is no gap between justified (or, reasonable) subjective probability and other concepts of probability in terms of its ability to provide assessments that are soundly based on whatever relevant information available. We also note that the challenges an expert faces in reporting probabilities apply equally to all interpretations of probability, not only to subjective probability
The consequences of understanding expert probability reporting as a decision
Full text linkIn this paper we reiterate that the personalist interpretation of probability is inevitable and as least as informed as any other allegedly more ‘objective’ definition of probability. We also argue that the problem faced by forensic scientists, the reporting on imperfect personal knowledge, in terms of probabilities, can be reconstructed as a decision problem. Tackling this problem through a rigorous decision theoretic analysis provides further argument in support of the view that optimal probability reporting is in terms of single numbers, not intervals
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
Letter to the Editor-Commentary on: Dror IG, Langenburg G. "Cannot decide": The Fine Line Between Appropriate Inconclusive Determinations Versus Unjustifiably Deciding not to Decide. J Forensic Sci https://doi.org/10.1111/1556-4029.13854. Epub 2018 Jul 5
No full textAnalysing and exemplifying forensic conclusion criteria in terms of Bayesian decision theory
No full textThere is ongoing discussion in forensic science and the law about the nature of the conclusions reached based on scientific evidence, and on how such conclusions – and conclusion criteria – may be justified by rational argument. Examples, among others, are encountered in fields such as fingermarks (e.g., ‘this fin- germark comes from Mr. A’s left thumb’), handwriting examinations (e.g., ‘the questioned signature is that of Mr. A’), kinship analyses (e.g., ‘Mr. A is the father of child C’) or anthropology (e.g., ‘these are human remains’). Considerable developments using formal methods of reasoning based on, for example (Bayesian) decision theory, are available in literature, but currently such reference principles are not explicitly used in operational forensic reporting and ensuing decision-making. Moreover, applied examples, illustrating the principles, are scarce. A potential consequence of this in practical proceedings, and hence a cause of concern, is that underlying ingredients of decision criteria (such as losses quantifying the undesirability of adverse decision consequences), are not properly dealt with. There is merit, thus, in pursuing the study and discussion of practical examples, demonstrating that formal decision-theoretic principles are not merely conceptual considerations. Actually, these principles can be shown to underpin practical decision-making procedures and existing legal decision criteria, though often not explicitly apparent as such. In this paper, we will present such examples and discuss their properties from a Bayesian decision-theoretic perspec- tive. We will argue that these are essential concepts for an informed discourse on decision-making across forensic disciplines and the development of a coherent view on this topic. We will also emphasize that these principles are of normative nature in the sense that they provide standards against which actual judg- ment and decision-making may be compared. Most importantly, these standards are justified independently of peoples’ observable decision behaviour, and of whether or not one endorses these formal methods of reasoning
The Dialogue Between Forensic Scientists, Statisticians and Lawyers about Complex Scientific Issues for Court
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
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