Dahlman analyzes the case with a version of Bayes’ rule that can handle dependencies. He claims that his method can help a fact finder avoid various kinds of bias in probabilistic reasoning, and he identifies occurrences of these biases in the analyzed decision. While a mathematical analysis may give a false impression of objectivity to fact finders, Dahlman claims as a benefit that it forces to make assumptions explicit, which can then be scrutinized.

The standard of proof in criminal trials should require that the evidence presented by the prosecution is robust. This requirement of robustness says that it must be unlikely that additional information would change the probability that the defendant is guilty. Robustness is difficult for a judge to estimate, as it requires the judge to assess the possible effect of information that the he or she does not have. This article is concerned with expert witnesses and proposes a method for reviewing (...) the robustness of expert testimony. According to the proposed method, the robustness of expert testimony is estimated with regard to competence, motivation, external strength, internal strength and relevance. The danger of trusting non-robust expert testimony is illustrated with an analysis of the Thomas Quick Case, a Swedish legal scandal where a patient at a mental institution was wrongfully convicted for eight murders. (shrink)

Arguments on legal evidence rely on generalizations, that link a certain circumstance to a certain hypothesis and warrants the claim that the circumstance makes the hypothesis more probable. Some generalizations are acceptable and others are unacceptable. A generalization can be unacceptable on at least four different grounds. A false generalization is unacceptable because membership in the reference class does not increase the probability of the hypothesis. A non-robust generalization is unacceptable because it uses a reference class that is too heterogeneous. (...) A biastriggering generalization is unacceptable because decision makers are inclined to overestimate the evidentiary value of membership in the reference class. A discriminating generalization is unacceptable because it puts members in the reference class in an unfair disadvantage. Research funded by the Swedish Research Council. (shrink)

According to Svein Eng there are propositions concerning the law which are descriptive as well as normative, but cannot be separated into one descriptive and one normative proposition. Eng calls these propositions “fused” (“sammensmeltede”). In Eng's theory a proposition with “fused modality” is partly descriptive and partly normative, but cannot be classified as a separable combination of a claim about what the law “is” and a claim about what the law “ought to be.” In a “fused” proposition modality is a (...) question of “degree.” The purpose of this article is to show why Eng's theory should be rejected. The introduction of “fused modality” adds nothing of value to legal theory. Eng claims to have discovered a class of propositions not previously accounted for, but this is not the case. The lawyer Eng talks about as making a “fused” proposition is simply a lawyer logically confused. (shrink)

An argument that makes use of a generalization activates the prototype for the category used in the generalization. We conducted two experiments that investigated how the activation of the prototype affects the persuasiveness of the argument. The results of the experiments suggest that the features of the prototype overshadow and partly overwrite the actual facts of the case. The case is, to some extent, judged as if it had the features of the prototype instead of the features it actually has. (...) This prototype effect increases the persuasiveness of the argument in situations where the audience finds the judgment more warranted for the prototype than for the actual case, but decreases persuasiveness in situations where the audience finds the judgment less warranted for the prototype than for the actual case. (shrink)

This book provides theoretical tools for evaluating the soundness of arguments in the context of legal argumentation. It deals with a number of general argument types and their particular use in legal argumentation. It provides detailed analyses of argument from authority, argument ad hominem, argument from ignorance, slippery slope argument and other general argument types. Each of these argument types can be used to construct arguments that are sound as well as arguments that are unsound. To evaluate an argument correctly (...) one must be able to distinguish the sound instances of a certain argument type from its unsound instances. This book promotes the development of theoretical tools for this task. (shrink)

"Philosophical Foundations of Evidence Law presents a cross-disciplinary overview of the core issues in the theory and methodology of adjudicative evidence and factfinding, assembling the major philosophical and interdisciplinary insights that define evidence theory, as related to law, in a single book. The volume presents contemporary debates on truth, knowledge, rational beliefs, proof, argumentation, explanation, coherence, probability, economics, psychology, bias, gender, and race. It covers different theoretical approaches to legal evidence, including the Bayesian approach, scenario theory, and inference to the (...) best explanation. The volume’s contributions come from scholars spread across three continents and twelve different countries, whose common interest is evidence theory as related to law"-- from publisher's website. (shrink)

Abstract. The analysis of legal statements that are made from an "internal point of view" must distinguish statements where legal obedience is accepted from statements where legal obedience is only assumed. Statements that are based on accepted obedience supply reasons for action, but statements where obedience is merely assumed can never provide reasons for action. It is argued in this paper that John Searle neglects this distinction. Searle claims that a statement from the internal point of view provides the speaker (...) with reasons for actions that are "self-sufficient" in the sense that they are independent of the speaker's beliefs and desires. This claim is mistaken. A statement that is based on assumed obedience is self-sufficient, but does not give reasons for action. A statement that is based on accepted obedience gives reasons for action, but these reasons are not self-sufficient. (shrink)

We investigate argumentation where an expression is substituted with a less precise expression. We propose that the effect that this deprecization has on the audience be called deprecization effect. When the audience agrees more with the less precise version of the argument, there is a positive deprecization effect. We conducted an experiment where the participants were presented with a court room scenario. The results of the experiment confirm the following hypothesis: If the participants find it hard to agree with the (...) precise version of the argument and accept the use of the imprecise term, they will agree more with the imprecise version of the argument. Furthermore, we show that a person who reacts in this way to deprecization commits the fallacy of equivocation. (shrink)

This article explores what ‘plausible’ means in statements about legal evidence and shows that it is highly ambiguous. Twelve different meanings of ‘plausibility’ are identified and distinguished from each other by definitions. Contrary to what has been claimed by some evidence scholars (Allen and Pardo, 2019), the article shows that all uses of ‘plausibility’ can be captured in terms of probability. The author also shows that the exposed ambiguity is deeply problematic for legal practice and legal scholarship. The fundamental principle (...) of justice that ‘like cases should be treated alike’ is endangered when the standard of proof is expressed in an ambiguous way, and the scientific testability of hypotheses about legal fact-finding is undermined when these hypotheses are formulated in ambiguous terms. (shrink)

In this paper we compare causal models with reason models in the construction of Bayesian networks for legal evidence. In causal models, arrows in the network are drawn from causes to effects. In a reason model, the arrows are instead drawn towards the evidence, from factum probandum to factum probans. We explore the differences between causal models and reason models and observe several distinct advantages with reason models. Reason models are better aligned with the philosophy of Bayesian inference, as they (...) model reasons for up-dating beliefs. Reason models are better suited for measuring the combined support of the evidence, and a prior probability of guilt that reflects the number of possible perpetrators is accommodated more easily with reason models. (shrink)