Human Deliberation in Fact-Finding and Human Rights in the Law of Evidence


Human Deliberation in Fact-Finding and Human Rights in the Law of Evidence



US LAW OF Evidence scholars concern themselves with constitutional protections associated with evidentiary rules. They do not generally pose the question whether a particular procedural rule establishes a legally-cognisable ‘human’ right, as opposed to a moral or political right. Analysis of rights is more familiar territory to legal theorists. In Justice for Hedgehogs1 Ronald Dworkin considers and rejects various standards for distinguishing human rights from political rights, including the arguments that human rights trump national sovereignty and that certain rights are especially important.2 On Dworkin’s account, human rights can be boiled down to just one basic abstract right, ‘a right to be treated as a human being whose dignity fundamentally matters’.3 Whilst breaches of political rights may involve injustice and moral error, violations of human rights imply nothing less than disdain for human dignity.

Hock Lai Ho, in his contribution to this collection, likewise depicts human rights as establishing fundamental minima, in the sense that they set the baseline for tolerable human conduct, not standards of excellence.4 He characterises the presumption of innocence as a human right, since it is not merely a default rule of criminal procedure, but also a check on the executive requiring production of evidence and proof of criminal charges. In the subsequent chapter, Mike Redmayne discusses the relationship between evidence law and human rights at its most practical.5 He argues that recognition of stronger confrontation rights in the United States and in the case-law of the European Court of Human Rights should not prompt English law to follow suit. Specifically, Redmayne argues that the right to confrontation does not require the exclusion of hearsay statements made by declarants who are genuinely unavailable at trial.

This chapter’s method is exploratory and interdisciplinary. It showcases behavioural science research on human cognition and draws out the implications of this neglected perspective for legal adjudication. The analyses of Ho and Redmayne will serve as a springboard for developing my central thesis, that better understanding of human cognition would promote improved trial outcomes. We assume that courts and lay fact-finders must resolve disputed questions of fact under conditions of infinite uncertainty, and where deductive entailment is an inadequate resource for enabling them to sort and evaluate the evidence. Predictable errors occur because the law of evidence fails to recognise that common cognitive strategies used by human beings in daily life do not map well onto trials.6 One example is systematic over-estimation of the weight of expert evidence.7 These types of considerations are pertinent to the success of legal fact-finding regardless of a particular procedural environment’s significant design features (eg whether the legal system is ‘adversarial’ or ‘inquisitorial’; whether or not criminal procedure is (partly) constitutionalised; whether or not there is a formal hearsay rule, etc).


Studies of human cognition offer distinctive and unique benefits for comparative or theoretical research. Some cultures have adversarial procedural systems; others do not. Some systems rely heavily on oral evidence, or on presentation of evidence and arguments within a relatively constrained time period. Others may consider adversarialism a mixed blessing at best, and juror participation in trials as misplaced amateurism. And, as comparative legal scholars know, the degree to which cultures differ in their views of authority is profound.8 However, as this volume indicates, comparative study may yield other insights when it operates from standpoints of commonality. Human cognitive abilities are one such source of commonality.

My focus is the extent to which the cognitive reality of decision-making (as opposed to arguments from process values or some other normative basis) may ground a right to require the adjudicator to gather or evaluate information in a particular way.9 The argument presupposes that human cognition is basic to any fact-finding or dispute resolution process and has important ramifications for substantive as well as procedural rights. In particular, what I call the ‘right to due deliberation’ in criminal adjudication requires that the prosecution gather and produce sufficient evidence, and that triers of fact consider the evidence before them diligently, relative to what is at stake for the accused. To the extent that particular items of evidence could lead to error through the application of commonplace cognitive strategies, the defendant may have a right to have the adjudicator subject that evidence to special processes or even exclude the evidence on the ground that any positive contribution the evidence might make to fact-finding would probably be outweighed by its cost in terms of increased risk of inaccuracy.

The point of adjudication is to determine which parties have the substantive rights they claim, or the extent to which one party’s rights should prevail. The strengths and weaknesses of the parties’ claims are normally initially uncertain: no party has a right that is clearly superior to any competing claim. Prior to the point of decision-making, adjudicators at most can perceive the values at stake in a particular party’s contentions, and the importance of the issues in light of those values and the likelihood that any facts the party alleges are true.10 To depict the cognitive reality of adjudication we must therefore speak of the values or importance of the issues at stake in particular legal proceedings, rather than trying to specify substantive rights.

For adjudicators to treat the defendant as one whose dignity fundamentally matters11 regard must be had to the possible importance of the claims and defences being adjudicated. Similarly, adjudicators should not use decision-making shortcuts that create unwarranted risks of error.


The most subtle, but also most powerful, constraints on human decision-makers are not limitations on their time, or material resources, but limitations on people’s abilities to process information and to maintain coherent belief systems. In light of these constraints, the use of strategies to allocate cognitive resources effectively is necessary for the integrity of all human dispute resolution. Decision-makers must allocate their resources among multiple tasks and problems. Accordingly, to enhance the likelihood of accurate fact-finding, legal rules should encourage decision-makers to allocate their cognitive resources relative to the problem-solving task or tasks at hand and so that criminal verdicts are not bought at the price of prejudice to the defendant, or recklessness in regard to her interests. This responds to Dworkin’s indispensible human rights criterion, that people must be treated in a manner consistent with their fundamental dignity.

Fact-finders are in a finitary predicament,12 a situation resulting from limitations on time, information, access to further information, and cognitive resources. Constraints on the ability of the adjudicator to process and evaluate information are of critical importance. They necessarily affect decisions regarding both historical facts and interpretation of legal criteria.13 These constraints put a premium on efficient use of scarce decision-making capacity and time. Research in cognitive psychology and related disciplines14 reveals limits on individuals’ mental ability to organise masses of data and to deploy those data to solve problems. Potential data overload constrains short-term or working memory.15 Although one’s working-memory capacity may vary according to the nature of the problem16 and between individuals,17 the limitations of human memory help shape the manner in which people perform any inferential task, including the interpretation of language.18 These constraints put a premium on efficient use of scarce decision-making capacity and time, and pose the danger of inappropriate decision-making strategies. At worst these can include guesswork.

Developing strategies to deploy decision-makers’ intellectual capacity most effectively should reduce inappropriate decision-making.19 For any given task, there may, in fact, be a repertoire of suitable strategies from which decision-makers can select one or more through modification or by combination. These strategies, including the revision of failed strategies,20 can be learnt from experience,21 or from others.22 For example, the cognitive trait that distinguishes chess masters23 and physics teachers24 from novices in their respective fields is their ability to perceive familiar patterns and use critical data to solve task-related problems. The possible lines of play on a chessboard, anticipating just the next two moves for each number on average one million; for three moves, one billion.25 Assuming that a chess master would take 10 seconds to consider each possibility afresh, and to consider that move’s effect on the opponent’s next two moves, comprehensive examination of alternatives would take approximately four months.26 Or to give an example more proximate to legal decision-making, simply checking 138 independent beliefs for logical consistency (without even attempting to use them to draw any new conclusions) would take the fastest serial computer longer than the history of the universe.27 The ability to seize upon the critical aspect of a problem and respond effectively to familiar patterns is indispensable to consistent success in dealing with large amounts of data.


In assessing the efficacy of decision-makers’ allocation of their decision-making resources, it is important to appreciate that they must consider not only possible inferences or inclinations but also counter-possibilities to inferences or inclinations in reaching a particular decision. Further, it is tolerably clear that decision-makers cannot, without employing appropriate strategies, consider all counter-possibilities. Even if a decision-maker had the cognitive resources to consider an infinite number of counter-possibilities,28 practical limitations mean that he or she, like the chess master, is unlikely to do so thoroughly.

The theoretical construct of a ‘schema’ (plural, ‘schemata’) is useful for understanding how we organise knowledge in our memory into strategies for solving problems, given the evident constraints on our ability to evaluate empirical data and maintain a completely coherent belief system.29 Schemata supply an index to our problem-solving procedures, and help us work out new protocols when necessary.30 We employ schemata to identify permissible inferences or conclusions on given information, to discern when more information is required before reaching a decision, and to diagnose incoherence in our thought processes.31 Schemata might be conceptualised as providing slots into which information can be fitted.32 If enough slots are filled (or preconditions are satisfied), a particular schema becomes operative. If it is well-adapted to the problem, the applicable schema may contain or refer to a procedure for solving it. More generic schemata might simply help us to determine that we should search for certain sorts of information,33 or that we should consider whether to employ one of a limited number of more specific cognitive strategies.

For a self-aware decision-maker, the availability of decision-making strategies is a two-edged sword. Without them, many decisions are made more difficult and in some contexts the resolution of complex issues with complete integrity can be impossible.34 However, schematic short-cuts are effective, but far from fool-proof. If a decision-maker selects the wrong schema from her personalised inventory, and is determined to stick with it, then a correct decision will either be impossible or, at best, a matter of good fortune. In addition, a decision-maker relying on schemata and other cognitive short-cuts must be alert to the potential fallibility of her understanding of relevant events and of relying upon analogical reasoning to extend a strategy to a new situation.35


Having been presented with significant information, the legal fact-finder acts rationally and in accordance with a defendant’s right to due deliberation if she explores counter-possibilities to the inferences the prosecution urges, to the extent that this approach is warranted by the interests at stake.36 Those counter-possibilities may be functions of new data, or of strategies the fact-finder has not previously considered, or combinations of the two. If the fact-finder fails to explore counter-possibilities appropriately—perhaps in reliance on the wrong cognitive strategy—she violates the right to due deliberation. She may act irrationally if she fails to allocate her resources in accordance with the relative importance of the tasks at hand. Finally, in the context of an episodic trial on the civilian procedural model, a decision-maker might reasonably conclude that the best use of her resources is to suspend judgment pending the acquisition of further information.37

It is one thing to say that people who use the sorts of reasoning strategies sketched above succeed in solving problems in their daily life. It is quite another to say that the same approach would be appropriate to decision-making that: (i) involves the rights and interests of other people and is determined according to criteria that may be subject to competing interpretations; (ii) must be based on incomplete information; and (iii) dramatically affects third parties if the decision-maker chooses to employ more thorough, elaborate or time-consuming processes.

Dworkin argues that denial of substantive rights through procedural failings constitutes moral harm; or at the least, failure by the adjudicator to accord the claimant equal treatment in the application of a particular legal standard.38 One might, of course, disagree with Dworkin’s notions about moral harm, but they usefully illustrate an important point. In the absence of any rule or determinate norms to guide or regulate cognitive processes in fact-finding, adjudicators would be free to utilise reasoning procedures that give short shrift to whatever values particular substantive rights entail. And that would be contrary to Dworkin’s conception of the basic human right to dignity. In a context where some form of harm might follow from incorrect adjudication of a claim of right, an adjudicator’s failure to conduct her decision-making process in light of the possible harm that might flow from incorrectly deciding the claim would, in effect, permit her to disregard that harm, or to employ some idiosyncratic reasoning strategy that was inappropriate in light of the stakes.39

Even so, there are limits on the resources we can expend on a particular trial. When there are competing claims on our cognitive resources, we must seek strategies not only for solving individual problems taken in isolation, but also for apportioning resources among multiple problems. It is unlikely that we can even state the expected utility of various decisions or resources with precision.40 Be that as it may, the limits and conflicting demands upon our resources still imply that judges should employ those resources (and guide jurors’ allocation of them) in light of the importance of the issues to be determined in the instant case and with attention to conserving resources for competing claims still awaiting adjudication.


Once proffered evidence or inferences satisfy threshold requirements of value or importance, the right to due deliberation entitles one to expect that an adjudicator will consider them to the extent warranted by the importance of the question on which they bear. One should be entitled to expect more thorough evidence-gathering and deliberation when more significant rights or interests are at stake, and somewhat less in other contexts.

Under the right to due deliberation, a criminal defendant is entitled to have the adjudicator consider whether the arguments and evidence advanced by the prosecution warrant a conviction in light of pertinent counter-possibilities consistent with innocence, and with scrutiny reflecting the importance of the claim or defence in question. This specification of the right to due deliberation is consistent with Dworkin’s contention that human rights require that people not be punished ‘except through procedures reasonably well calculated to protect the innocent’.41

Any number of evidentiary rules in adversarial jurisdictions reflect a desire that fact-finders be as completely well-informed as reasonably possible, not only in the sense that they should be provided with all worthwhile information, but also that they should receive second-order information about the probative worth of at least some of the evidence adduced in the trial.42 Factual pre-conditions for the admission of evidence normally require proof that proffered evidence has sufficient probative value to make its reception worthwhile, that it will assist in the evaluation of other evidence, or both.43 To similar effect, the best evidence or original document rule creates an incentive for production of an original or authentic duplicate,44 which makes accurate evaluation of the document less complex45 and corroborates the proffering party’s claims for its provenance, which in turn serve to reassure the court that evaluation of the document is warranted by its importance for one or more issues at trial.