Abstract

This thesis examines deliberation in legal proceedings. Legal deliberation is conceived of as the procedures by which a judge, jury, or other rational deliberating agents arrive at a verdict. Legal deliberation involves deliberation about laws and about facts. This thesis is concerned chiefly with deliberation about facts and how value considerations impinge on deliberation about facts. In legal proceedings there are a number of principles that are generally accepted, although their application varies according to whether the procedure is criminal, civil, administrative or other. These principles include: an accused must be proved to have committed an act according to a given standard; a person is presumed innocent until proven guilty; a proposition may be presumed by making an inference from a basic proposition which has been proved; only relevant evidence may be admitted; only reliable evidence is accepted; evidence may be accepted on the basis of judicial notice; and unreliable evidence may be admitted if corroborated. Some less familiar principles are that proved propositions are consistent; all the elements of a case need to be proved in order for the case to be proved; a proposition at issue is not proved unless it is based upon complete evidence; and that the degree of persuasion that a deliberator has towards a proposition at issue be equal to the objective probability of that proposition. Although these principles are generally accepted the intepretation of these principles is unsettled. This thesis attempts to give an interpretation of these principles which justifies them. All interpretations have in common, I hold, that a rational agent has principles for modifying his deliberative state given new evidence. The deliberative state of an agent consists of a set of elements where B is the agent's degree of belief over a set of propositions S; K is a subset of S — the full or accepted beliefs; D is the agent's degree of desirability over propositions in S; ⁺ is a dynamical principle of deliberation which determines how values for B, and D change over time. The desires of the agent are taken to be a reflection of the values inherent in legal principles. A traditional principle is that in order to convict someone it must be proved that the accused committed the alleged act. There is little agreement, however, about what is involved in proving that a person has done something. There are two main theories which are used in law. One theory, the Austinian theory, takes an action to be a bodily movement that is voluntary. A second, wider view is that an action includes the bodily movement, consequences, relevant circumstances and voluntariness, and perhaps other elements, such as omissions, and things that happen to one, but not a mental event. I argue that an action is a part of a sequence of causally related events. It is that part of the sequence with the properties that are represented to the agent in his causally efficacious mental state. The interpretation of "prove" in the last cited principle is also unsettled. All views hold that, in some sense, a proved proposition be sufficiently probable. There are five views of probability that I canvass: the logical view, the subjective view, the relative frequency view, the chance view and the epistemic view. I argue that the epistemic view is particularly suited to legal reasoning. On this view probability is conceived as a mind independent logical relation between evidence admitted and the conclusion reached on the basis of that evidence. Probability also reflects the underlying chance of single events and so applies to individual actions. The traditional practices have been interpreted as the dynamics of deliberative states. There are two plausible models of these dynamics: Bayesian and non-Bayesian. On Bayesian theories all changes of belief are by Bayes' theorem or generalizations thereof. On a non-Bayesian view beliefs are changed by accepting new beliefs, conjoining them with the old beliefs, and modifying the old beliefs on the basis of the new ones. As an intepretation of legal deliberation the Bayesian view has a number of disadvantages. Among other difficulties I survey, on the Bayesian view one can not consider a case proved if all the elements of a case are proved, and one cannot regard a proved proposition at issue as true. Hence I reject the Bayesian theory. The principle that a person is proved to have committed an act if it is sufficiently probable that he committed such an act gives rise to a difficulty. Ultimately the problem amounts to how a theory of deliberation can meet three principles of legal reasoning: the deliberating agent's beliefs are consistent, the agent believes a proposition A if the probability of A is sufficiently high, and if the agent believes A and believes B then he believes. I show how this problem is resolved by requiring probability to be resilient. A person is proved to have committed an act if the probability of having committed that act reaches an appropriate standard of proof. But what is the standard that is at issue here? If the judge is a utilitarian, for instance his desire function must meet the constraint that it equals the average desires of all other agents. In the final chapter I argue that a utilitarian rationale for standards of proof violates a person's right not to be convicted if innocent. This is due to the fact that a person can be convicted by a utilitarian deliberator even though it is more probable than not that he did not commit the alleged offence