Theorising Evidence Law

Abstract—

What does it mean for a specialist department of legal studies, such as the Law of Evidence, to have, or to acquire, ‘philosophical foundations’? In what sense are the theoretical foundations of procedural scholarship and teaching distinctively or uniquely philosophical? The publication of Philosophical Foundations of Evidence Law (OUP, 2021), edited by Christian Dahlman, Alex Stein and Giovanni Tuzet, presents a valuable opportunity to reflect on these existential questions of disciplinary constitution, methodology and design. This review article critically examines the volume’s idiosyncratic selection of topics, structural taxonomy, epistemological priorities, and enigmatic thesis that modern evidence law is turning from rules to reasons as its organising intellectual framework. Whilst the volume is impressively interdisciplinary and cosmopolitan in authorship and outlook, some doubts are expressed about its implicit US orientation, limited engagement with institutional or doctrinal details, and marginalisation of normative criminal jurisprudence.

1. Philosophical Treatment: ‘You get an’ology, you’re a scientist!’¹

To the extent that philosophical theorising is a mark of disciplinary sophistication, self-confidence and growing maturity, Evidence specialists should welcome the appearance of Philosophical Foundations of Evidence Law (PFoEL), edited by Christian Dahlman, Alex Stein and Giovanni Tuzet. This is, by my count, the nineteenth instalment of OUP’s Philosophical Foundations of Law series, published since 2009, and already elevating topics considerably newer and more niche than the Law of Evidence to its pantheon of philosophical self-consciousness.² Let us not be churlish: late is better than never.

The series ‘aims to develop work at the intersection of legal philosophy and doctrinal law … provid[ing] a roadmap of current philosophical work in the field to lawyers and philosophers looking for high quality new work and … a stimulus for further research’. The editors explain in their—regrettably brief—Introduction that ‘The principal idea of this project was to assemble and present the major philosophical and interdisciplinary insights that define evidence theory, as related to law’.³ Any aspiration to define must confront terminological nuances that are more than merely semantic. ‘Evidence theory’, on any competent definition, is plainly not isomorphic with substantive evidence law, nor does it replicate that slice of common law education conventionally styled Law of Evidence. Scholars conceptualising ‘evidence and proof’ move expansively tend to regard fixation on ‘law’ as unhelpfully narrow or distracting.⁴ The uses—and abuses—of evidence in legal contexts is only a small, institutionally differentiated and somewhat specialised department of the social uses of evidence (aka ‘data’ or ‘information’) more generally.⁵ Evidence Law in the classroom can be a ‘multidisciplinary subject’ in ways that evidence law in litigation practice cannot, indeed should not, be.⁶

The editors’ reference to ‘philosophical and interdisciplinary insights’ implies, correctly in my view, both that some philosophising is internal to the discipline of law (and thus not strictly interdisciplinary) and that some salient interdisciplinary insights are not necessarily philosophical. Threshold questions that may play on Evidence scholars’ minds include: how is the ‘philosophy of evidence law’ related to ‘evidence theory’, and what can either or both contribute to the prosaic activities of analysing, criticising and applying evidence law in academic scholarship, university teaching and legal practice? The editors situate their project both temporally and intellectually as a continuation of 1980s’⁷ New Evidence Scholarship,⁸ prior to which ‘Evidence theory as related to law stayed mostly dormant’.⁹Dormant is apt, because the New Evidence Scholarship was partly a revivalist rediscovery of older programmatic texts.¹⁰ Plausibly enough, the editors single out Twining’s Theories of Evidence¹¹ and a Boston University Law Review symposium on ‘Probability and Inference in the Law of Evidence’¹² as watershed moments in Evidence law theory’s evolution: ‘These publications have irreversibly changed the direction of the study of evidence by shifting evidence scholars’ focus from rules to reasons.’¹³ This is an intriguing but largely unelaborated claim, which could only be vindicated (or not) by individual chapters in the volume.¹⁴

The proposition that modern evidence law has become progressively less rule-focused resonates with experience in England and Wales: some old evidentiary rules have been abolished; others have been reformed in ways that afford more latitude to general principles and judicial discretion in their application; still other norms are not evidentiary ‘rules’ in the traditional legal sense.¹⁵ Whether or how the pivot away from rules has been accompanied by a newfound interest in ‘reasons’ as an organising intellectual framework is harder to judge. Notwithstanding scattered signposts in specialist literature,¹⁶ one might suppose that traditional concepts such as ‘fact-finding’, ‘inference’, ‘proof’, ‘litigation’ or ‘legal process’ remain more intuitive and intelligible to legal scholars. According to the editors, ‘The shift from rules to reasons was transformative along two dimensions: interdisciplinarity and internationalization’:

The realization that reasons moving the factfinding process forward are antecedent to, and consequently more important than, evidentiary rules has opened up new paths of inquiry that connected adjudicative factfinding to epistemology, mathematics, economics, psychology, sociology, political morality, and linguistics and led to further and richer explorations of how theories of probability and induction affect the understanding and reform of the law of evidence. The primacy of reasons has also created a sizable common ground for theorizing for evidence scholars from different countries. With a focus on reasons rather than rules, the differences between factfinding in the more regulated Anglo-American systems vis-à-vis the freer European systems—once understood as dramatic—became less important.¹⁷

That a landmark publication written in English should be edited by a Swede, an Israeli and an Italian is a powerful testament to Evidence scholarship’s cosmopolitan aspirations. The volume’s contributors are ‘spread across three continents and domiciled in twelve different countries’,¹⁸ and include numerous voices from beyond the common law orbit. Nonetheless, a third of the 32 contributors is US-based; plus Alex Stein taught in US law schools for 20 years before being appointed to the Israeli Supreme Court. This geographical concentration intimates a version of anglophone Evidence theory skewed towards Anglo-American Evidence theory, with a pronounced New World accent.

2. Structural Taxonomy: The Disciplinary Ins and Outs

After its terse Introduction, PFoEL comprises 26 chapters divided into seven parts, each containing between two and six chapters. The overall page count is 417, bulky for a monograph but relatively slim for a ‘handbook’-style Cook’s Tour of disciplinary highlights. Part I has four chapters addressing ‘Evidence, Truth, and Knowledge’. Part II, on ‘Law and Factfinding’, is the longest subdivision, numbering six chapters. Part III contains three essays on ‘Evidence, Language, and Argumentation’, linking directly into Part IV’s trio of chapters on ‘Evidence and Explanation’. Part V moves the discussion on to ‘Evidence and Probability’, with four entries, followed by the shortest subdivision, Part VI, comprising a pair of essays on ‘Proof Paradoxes’. Finally, Part VII returns to somewhat more tangible practical concerns with four chapters on the theme of ‘Biases and Epistemic Injustice’. The rationale for this selection and taxonomic arrangement are not always readily apparent. The chapter by Lena Wahlberg and Christian Dahlman on ‘The Role of the Expert Witness’, for example, concludes Part I’s epistemological discussion but is largely an exercise in institutional jurisprudence,¹⁹ supposedly the topic of Part II. Then again, ‘Law and Factfinding’ is so generalised that virtually any chapter in the book could plausibly appear there. Why is Part IV framed in terms of ‘Explanation’ rather than ‘Proof’? Does this terminology reflect the disciplinary assumptions of argumentation theorists in preference to concepts more familiar to lawyers and legal practice? Forensic probability is undeniably prominent in modern scholarship and legal practice, but the space it occupies in this volume feels indulgent. Affording ‘Paradoxes of Proof’ its own—albeit short—part seems positively eccentric, when these puzzles have previously attracted minute dissection for dubious explanatory profit.²⁰

Evidence teachers might be puzzled by some notable absences. Only one of the seven parts expressly mentions ‘law’ (or any related juridical concept), and most of the material in this part is actually concerned with forensic process and the evaluation of evidence rather than addressing normative, doctrinal or jurisprudential questions. With a handful of exceptions,²¹ individual chapters largely eschew common law textbook staples. There is nothing substantial on presumptions, character evidence, witness competence, testimonial privileges, public interest immunity, rape shield, special measures for vulnerable or intimidated witnesses, memory refreshing, judicial notice, previous judgments as evidence, fair trials, confessions, privilege against self-incrimination, eyewitness identification evidence or corroboration, and little discussion of broader procedural or institutional contexts. Gabriel Broughton and Brian Leiter in their chapter caution that ‘accurate adjudication depends on more than evidence law. It depends, for example, on civil and criminal procedure … The study of evidence law thus falls into place as one component of the broader project of studying adjudication’.²² Contributors across the volume freely help themselves to illustrations and examples drawn from litigation process—typically concerning contested trials—so it cannot be said that the editors’ or authors’ conceptions of ‘evidence’ or the disciplinary field of ‘Evidence’ systematically exclude ‘procedure’. Those who like to credit Bentham as the father of modern Evidence studies²³ might be well advised to follow his lead in conceptualising judicial evidence as a subpart of legal procedure, inviting further reflection on nuances of institutional practices and traditions.

Rather than the traditional textbook fare, chapter titles serve up ‘cost–benefit analysis’, ‘scenario theory’, ‘reference classes’, ‘Bayesianism’, ‘naked statistical evidence’, ‘de-biasing’, ‘epistemic injustice’ and ‘the problem of the prior’. Unless these choices are completely arbitrary or idiosyncratic, they should be related to disciplinary objectives—which require articulation and defence. Assuming some general relation between Evidence theory and Evidence Law/evidence law, such that the former is, in some sense (philosophical or more broadly theoretical) foundational for the latter, Evidence scholars and teachers are entitled to ask how these connections are being forged.²⁴ Bluntly, if theorists’ analyses and solutions are mainly concerned with addressing theorists’ problems, why should that theoretical activity exert any claim on the time and attention of legal practitioners or (doctrinal) evidence scholars? In the absence of more explicit editorial elucidation, initial puzzlement is predictable and some potential readers’ motivation might expire before enlightenment strikes.

3. Epistemology Rules

Part I trumpets the primacy of epistemological concerns. First up, Hock Lai Ho’s precise and considered essay on ‘Evidence and Truth’ argues that trials aim at ‘truth’ in the ordinary sense, dispensing with adjectival qualifiers such as ‘legal truth’, ‘formal truth’ or ‘procedural truth’ as unhelpful. Although ‘the trial is vastly different from a scientific or historical inquiry’,²⁵ nonetheless, Ho insists, ‘adjudication of factual disputes, which is the definitive business of the trial, is aimed at ascertaining the truth’.²⁶ In the following chapter, Gabriel Broughton and Brian Leiter present the case for ‘The Naturalized Epistemology Approach to Evidence’, which takes truth-finding goals for granted and sets out to test existing institutional performance employing empirical social science research methods. For example, psychologists conduct mock jury studies to interrogate evidentiary doctrines, identify practical shortcomings and propose institutional reforms to enhance evidence law’s ‘veritistic’ (truth-conducive) qualities. Advocating scientific investigation over normative theorists’ armchair speculation, Broughton and Leiter insist that—sometimes exaggerated—problems of ecological validity and other methodological limitations can, in general, be overcome through superior research designs. Their own illustrations of naturalised approaches to eyewitness testimony and character evidence are thoughtful and modestly circumspect in their recommendations. The discussion, however, proceeds on the footing that evidence law means the US Federal Rules of Evidence, and does not seem to have any specifically philosophical content. Charitably, the point is that philosophical analysis is required to clarify the concepts employed in framing empirical inquiries,²⁷ though this is not expressly stated.²⁸

In ‘Proven Facts, Beliefs, and Reasoned Verdicts’, Jordi Ferrer takes aim at the ‘subjectivist’ conception of factfinder belief. His reading of American legal sources leads him to conclude that common lawyers’ probabilistic conceptions of standards of proof are no less subjectivist than the classical intime conviction prevalent in modern continental European legal systems. Subjectivism in decision standards is bad epistemology,²⁹ and moreover, Ferrer argues, it is incompatible with giving reasons for adjudicative determinations as required by procedural due process and (European) human rights law. This chapter vindicates the editors’ promise of an Evidence (theory) scholarship invigorated by comparative jurisprudence, and does more than most to illuminate the somewhat enigmatic claim that Evidence law has shifted, or should shift, its primary focus from rules to reasons. Ferrer’s central argument is restricted to adjudicative contexts, such as civil litigation, in which the duty to give reasons prevails, and therefore does not encompass criminal jury trials in England and Wales. Ferrer ventures that ‘in English-speaking countries … the current discussion is not so much about whether or not reasons should be given for decisions as about how far this duty extends’.³⁰ Mandating juries to deliver reasoned verdicts is an interesting thought experiment with credible proponents,³¹ but there are telling grounds for scepticism³² and no proximate likelihood of reform. Whilst Ferrer tends to assimilate ‘English-speaking literature’ to US jurisprudence and commentary, the standard of proof now officially endorsed in English criminal trials is not even superficially probabilistic.³³ Moreover, it is difficult to see how an entity like a jury, charged with rendering its collective decision,³⁴ could have ‘subjective beliefs’ akin to an individual mind.

Wahlberg and Dahlman’s essay on ‘The Role of the Expert Witness’ completes Part I’s quartet. Cutting through abstruse theoretical controversies, it engages directly with the epistemological credentials of institutional practices. Legal scholars and practitioners will already know that expert witnesses should assist the factfinder, stick to the question(s) assigned and avoid expressing views on either questions of law or ultimate issues of fact.³⁵ Interdisciplinary conversation works in both (or multiple) directions, however, and these juridical axioms may be less widely appreciated by expert witnesses and other non-lawyers. Operating within a broadly ‘Bayesian’ intellectual framework, Wahlberg and Dahlman contend that ‘The role of the expert witness in the evaluation of evidence is limited to how strongly the evidence supports the hypothesis … To speak on the likelihood ratio and be silent on the posterior probability’.³⁶ Accepting (as one should) that Bayesianism is logically sound, practical jurisprudence is always mediated by institutional realities, calling for granular engagement with particular legal jurisdictions and regulatory structures. For example, there is at least a fighting chance of trying to explain to professional judges why they should not confuse the probability of the evidence assuming the truth of the hypothesis (assessing ‘weight of evidence’, as expressed by the likelihood ratio)³⁷ with the probability of the hypothesis in light of the evidence (the disputed facts in the litigation),³⁸ but there is virtually no chance of trying to explain this to a lay jury during a contested criminal trial.³⁹ Lay factfinders must be insulated from illegitimately ‘transposing the conditional’⁴⁰ by other procedural safeguards. Lurking complexities are magnified by comparative lenses,⁴¹ and cannot always be resolved simply by appealing to general (epistemic) principles.

With epistemology as its guiding principle and method, Evidence law theory can be simultaneously philosophical, interdisciplinary and cosmopolitan, but this methodological polymorphism comes at a price. Common law orthodoxy, as reflected in successive editions of Cross on Evidence and the US Federal Rules of Evidence (FRE), presupposes a ‘trans-substantive’ epistemic disciplinary foundation, but modern English law does not.⁴² Rather, criminal procedure and evidence in England and Wales is effectively a different disciplinary specialism to civil procedure,⁴³ and the doctrinal bridge which traditionally linked the two parts is increasingly slender and rickety. When epistemology supplies the primary analytical lens and organising taxonomy, the gap between Evidence Law theorising in the classroom and applied evidence law in the courtroom almost inevitably widens. This fissure risks alienating law teachers aiming to inculcate professional skills and provide students with a sociologically realistic picture of litigation practice in their own jurisdiction. For all that comparative studies are invariably enriching, theorising indexed to local doctrine will, in a world of opportunity costs, predictably trump theories adapted to foreign law and practice.

4. Looking for Law

The orthodox ‘Thayerite’ conception of evidence law has long been criticised for its obsession with questions of admissibility, or ‘exclusionary rules’, to the neglect of broader issues of relevancy, inference, proof and fact-finding.⁴⁴ Featuring only two chapters (out of 26) taking exclusionary rules as their primary theme, PFoEL might be suspected of a rather dramatic over-correction.

‘Jeremy Bentham, one of history’s great haters, hated many things, and among them was the law of evidence’,⁴⁵ writes Frederick Schauer in his entertaining chapter on ‘The Role of Rules in the Law of Evidence’. Schauer poses the question why, despite the apparent common sense of Bentham’s ‘free proof’ antinomianism, ‘the law of evidence … remains substantially an affair of rules’.⁴⁶ Schauer is unpersuaded by standard rationalisations implying that jurors cannot be trusted with problematic evidence.⁴⁷ After all, professional judges may be no less susceptible to rationality lapses and cognitive biases, potentially inverting the Benthamite logic: perhaps we need more exclusionary rules to neutralise the infirmities of judicial reasoning. More fundamentally, Schauer argues, untrammelled official discretion in adjudication is incompatible with the rule of law,⁴⁸ and this foundational normative commitment should shift the burden of argument to modern-day proponents of Bentham’s ‘natural system’ of common sense inference. To the contrary, ‘perhaps it is the free proof tradition rather than the rule-based tradition that is in need of serious reconsideration’.⁴⁹

In the following chapter, Jules Holroyd and Federico Picinali explore ‘whether integrity plays a meaningful role as a standard of conduct for the criminal justice authorities, with specific regard to the gathering and the use of evidence’.⁵⁰ Aligning themselves with sceptical sentiment⁵¹ and to ‘curb the growing enthusiasm for integrity’,⁵² they develop their intuition⁵³ that appeals to ‘integrity’ in evidentiary discourse are superfluous and obfuscating. Meticulous conceptual analysis yields no definitive conclusion: ‘Our aim is not to claim that integrity is a useless tool in theorizing about, and in implementing, criminal procedure; rather, it is to show the challenges faced, and as yet unmet, by proponents of integrity.’⁵⁴ As it happens, I anticipate that this challenge can be met, by conceptualising ‘integrity’ as an integrative ideal⁵⁵ and practical attitude rather than as another freestanding exclusionary rationale. Holroyd and Picinali acknowledge that this conception, which they associate with ‘balancing’, is not vulnerable to their main conceptual critique, but add, reasonably enough, that further implications ‘would require careful scrutiny’.⁵⁶

Alongside several other excellent contributions of which space precludes discussion,⁵⁷ these two chapters distinguish themselves as genuine efforts to connect legal doctrine with its philosophical foundations.⁵⁸ They exemplify and intimate the further possibilities of a distinctively jurisprudential reconstruction of (criminal) evidence and procedure.

5. Arguments, Reasons and Proof

Parts III and IV are devoted to argumentation theory, a somewhat arcane subfield of philosophy, which originally grew out of a reaction against the strictures of formal logic⁵⁹ and subsequently developed its own interdisciplinary debates with contributions from computer science, AI, cognitive psychology, rhetoric, linguistics and narratology, amongst others.⁶⁰ Overlapping with Part V’s exploration of (Bayesian) probability and the logic puzzles dissected in Part VI, fully 12 of the book’s 26 chapters focus on arguments.

Floris Bex’s refreshingly non-technical essay on ‘Argumentation and Evidence’ affords an exemplary introduction to this literature.⁶¹ Proceeding from the truism that ‘Argumentation is central to legal and evidential reasoning’,⁶² Bex outlines ‘how arguments based on evidence to conclusions in a case can be built, how these arguments can be attacked and defended against counterarguments, and how generalizations can be used and analyzed in argumentation’. He concludes by briefly considering some methodological limitations. One problem is that arguments tend to be linear and schematic (as their graphical representations vividly show),⁶³ at least compared to the more richly articulated ‘stories’ or ‘narratives’ that human reasoners find naturally appealing.⁶⁴ This theme is developed by Anne Ruth Mackor and Peter van Koppen in their chapter on ‘The Scenario Theory about Evidence in Criminal Law’.⁶⁵ A second, well-rehearsed criticism of argumentation analysis is that it does not directly generate criteria of probative value or ‘weight’ of evidence, prioritising logical relations above the quality of inferential conclusions. Argumentation theory insists that inductive inferential reasoning is not automatically fallacious simply because its conclusions are defeasible.⁶⁶ All empirical propositions are vulnerable to sceptical doubt and any belief about empirical facts may be mistaken, which is just another way of saying that all empirical inference is probabilistic. Forthwith to the topic of Part V, ‘Evidence and Probability’.

In ‘The Logic of Inference and Decision for Scientific Evidence’, Franco Taroni, Silvia Bozza and Alex Biedermann clarify the problem of reasoning under uncertainty in legal proceedings employing the tools of probability, especially subjective Bayesianism, as a framework for rational inference in forensic science. This commendably accessible contribution highlights the distinction between inference and decision, the conflation of which has traditionally bedevilled scientific evidence and expert witness testimony.⁶⁷ ‘The role of probability’, they explain, ‘is nothing less than to ensure logical reasoning’:⁶⁸

Bayes’ theorem specifies how to re-organize one’s state of mind based on new data, that is how to update initial beliefs (i.e., prior to data acquisition) about propositions of interest. This idea of updating beliefs in the light of new information is conceptualized in terms of the likelihood ratio, a rigorous concept for a balanced measure of the degree to which particular evidence is capable of discriminating between competing propositions put forward by parties at trial.⁶⁹

This chapter promotes critical understanding of the conceptual foundations and logic of probabilistic reasoning by way of antidote to rote learning of formal axioms and parroting mindless mantras. Forensic scientists are not necessarily any more proficient in probability or statistics than lawyers. Clarifying institutional roles and responsibilities in legal proceedings (already stressed by Wahlberg and Dahlman) helps to explain why ‘claims by scientists regarding the use of formal methods of reasoning cannot easily be carried over to the conceptual problems encountered by lawyers and, hence, are met with skepticism’.⁷⁰ In ‘Bayesianism: Objections and Rebuttals’, Norman Fenton and David Lagnado expound more technical features of subjective Bayesian reasoning and advocate formal modelling of likelihood ratios through Bayesian networks employing computational algorithms.⁷¹ They urge that ‘Proper use of Bayesian reasoning has the potential to improve the efficiency, transparency, and fairness of criminal and civil justice systems’,⁷² not least by neutralising pervasive reasoning errors, including the notorious ‘prosecutor’s fallacy’.⁷³ The Bayesians do not have it all their own way. Having catalogued the errors of ‘probability theorists’ (who would be wrong even if they were right⁷⁴) in the previous part, Mike Pardo and Ron Allen conclude Part V, with their second contribution, on ‘Generalizations and Reference Classes’, by larding on further criticism: ‘Due to the epistemological limitations flowing from the reference-class issue, mathematical models do not very well capture the probative value of evidence.’⁷⁵

Without becoming embroiled in complex and long-running controversies, four brief observations are pertinent. First, whilst probability undoubtedly merits discussion in a book on the philosophical/theoretical foundations of evidence law, the extent of the coverage relative to other topics foreshortened or omitted entirely feels unbalanced. Secondly, to the extent that some theoretical debates or ‘paradoxes’⁷⁶ are purely theoretical, their claims to foundational status for evidence law appear dubious.⁷⁷ It strikes me, for example, that the so-called ‘problem of the prior’⁷⁸ is only a ‘problem’ for committed legal Bayesians, leaving conventional jurisprudential wisdom untroubled.⁷⁹ Thus, Dahlman and Kolflaath’s solution resembles the logic of undergoing eye surgery to compensate for wearing dark glasses. Why not simply ditch the theoretical spectacles and pre-empt excruciating correctives?

Thirdly, however, it does not follow from the fact that terms such as ‘subjective Bayesianism’,⁸⁰ ‘likelihood ratio’,⁸¹ ‘reference class’⁸² or, indeed, ‘probability’ are not common currency in criminal litigation or doctrinal evidence law scholarship that they are irrelevant to practical institutional concerns. In fact, forensic scientists and other expert witnesses are already routinely employing these concepts and formulae in their casework, so lawyers and judges must educate themselves and strive to keep up. Probabilistic thinking and reference class problems are inherent features of human rationality, cognition, inferential reasoning and decision making, springing notorious traps on the unwary. These banana skins of thought do not vanish just because we choose to ignore them.

A fourth observation further interrogates the vaunted priority of ‘reasons’ over rules in theorising evidence law. Argumentation theorists and epistemologists⁸³ distinguish between contexts of inquiry and contexts of justification, roughly, between looking for, gathering, organising and analysing evidence on the one hand and evaluating, forming beliefs or making decisions on the basis of evidence—evidence-based beliefs or decisions—on the other.⁸⁴ For decisions to be rational, they must be reasoned. So contexts of justification are fundamentally concerned with reasons. If the question is straightforwardly one of belief, then rationality demands that one should believe what one has most reason to believe; and for many (admittedly not all) questions, the best evidence will give the best reasons, or ‘epistemic warrant’, for belief (evidentialism). If, on the totality of evidence, it looks like p is true,⁸⁵ you should (rationally) believe p. In the context of legal adjudication, the best epistemic warrant for the tribunal’s decision is the best evidence, or at any rate sufficient evidence to satisfy the applicable proof threshold—in legal parlance, the burden and standard of proof.⁸⁶ When legal factfinders are called on to explain the reasons for their decisions, they are enjoined to explain what evidence they found compelling in supporting particular factual inferences, ultimately leading to the resolution of litigated claims or allegations—Wigmore’s ‘ultimate probandum’.

If we focus on contexts of justification, and more specifically on the evidential adequacy of trial verdicts, ‘reasons’ can be theorised as more fundamental in legal adjudication than (doctrinal) rules. Practising lawyers and legal scholars, however, currently think in terms of ‘proof’ rather than ‘reasons’, requiring an effort of translation from orthodox terminology and intellectual frameworks. But if, as it seems, these alternative conceptual schemas are linguistically fungible, ‘Evidence and Proof’ would be a more transparent and intelligible theoretical framing than ‘Evidence and Reasons’. Moreover, Evidence law as traditionally understood in UK jurisdictions is not much concerned with contexts of justification, because jury verdicts are not publicly reasoned⁸⁷ and, even post-Human Rights Act 1998, magistrates’ courts’ decisions are sparsely reasoned and of limited doctrinal interest. Justification in orthodox common law evidentiary thinking mostly relates to judicial rationales for the development and application of evidentiary rules, not to the rationality of fact-finding. Justification in the common law world, in other words, traditionally concerns law, not facts. Relatedly, legal argumentation in relation to evidence is generally conceived as referring to arguments addressed to judges about the law, nowadays addressing forensic reasoning rules as well as questions of admissibility.⁸⁸ If the philosophical/theoretical foundations of Evidence Law are primarily orientated to contexts of justification, it remains unclear how they can be foundational for common law evidence.

6. More Institutional Bias

Part VII extends the volume’s epistemological framing into more concrete applications. Reprising the naturalised approach championed by Broughton and Leiter, Justin Sevier suggests that ‘Empirical psychology is a natural fit for understanding the law of evidence but is also substantially at odds with it’,⁸⁹ giving rise to ‘methodological and philosophical challenges’.⁹⁰ Empirical psychology is a ‘scientific discipline [whose] goal is to discover truth’. Trial rules of evidence, by contrast, ‘routinely balance the factfinder’s quest for the truth with other policy considerations, including the procedural rights of criminal defendants and the protection of important societal relationships’, leading to the exclusion of ‘otherwise highly probative information … potentially at the expense of decision accuracy’.⁹¹ The ‘disconnect’⁹² that Sevier is describing is only elliptically ‘philosophical’. A more straightforward jurisprudential analysis is that adjudication serves normative ends, to which accurate fact-finding is a (major) functional contributor rather than a dominant purpose. The point of adjudication is to do justice according to law. This ordering of priorities is obscured by assuming the centrality of accurate fact-finding and treating all other ‘policy’ factors as side-constraints potentially detracting from (‘at the expense of’) factual rectitude, in the manner of traditional Law of Evidence scholarship and its US FRE iteration in particular.⁹³ Important normative and jurisprudential questions that, to my mind, ought to be central to theorising about judicial evidence are mostly absent from the relentless truth-instrumentalism of epistemic priority.⁹⁴ Traditional common law Evidence scholarship gravitated towards rules with obvious epistemological salience, such as the hearsay prohibition,⁹⁵ whilst neglecting foundational features of criminal procedure, including the presumption of innocence, the privilege against self-incrimination and the right to a fair trial. A more comprehensively normative theoretical framework, still incorporating significant epistemological components, could claim greater fidelity to evidence law as practised (at least in my jurisdiction) and cast Evidence law theory in a substantially different light.

None of which directly contradicts Sevier’s (or Broughton and Leiter’s) project of investigating the adequacy of evidence law’s empirical assumptions utilising the tools of experimental psychology and social science,⁹⁶ or denigrates reformist aspirations to improve verdict inaccuracy insofar as data and proposals legitimately relate to epistemic objectives. Conversely, ‘scientific’ methods cannot displace or circumvent normative (jurisprudential or political morality) arguments on pain of naturalistic fallacy. Sevier assumes the FRE and US adversarial litigation as the default referents of ‘evidence law’ and legal process. I am sceptical about his assertion that ‘evidence law is, at its core, deeply rooted in psychology’,⁹⁷ but it is hard to quibble with Sevier’s balanced evaluations of the accumulating corpus of psychological research bearing on eg character evidence, hearsay, witness impeachment and scientific evidence, or with his cautious advice for policy makers. ‘Whether those rule-makers will (or should) listen is a complex question’,⁹⁸ he volunteers, disarmingly. Furthermore, given ‘current issues in psychology—including a renewed interest in the replicability of prior studies’:

evidence rule-makers may be cautious even of the clear conclusions from this body of work. It may behoove psychologists to consider supplementing these findings with field research, including data collected from real trials.⁹⁹

Where Sevier is cautiously optimistic about the prospects for psychologists informing ‘legal policy-makers about the wisdom of many evidentiary rules’,¹⁰⁰ the tone of Frank Zenker’s contribution on ‘De-biasing Legal Factfinders’—the book’s final chapter—is pessimistic. Perplexity regarding ‘unconscious bias’ has lately generated widespread public debate and the search for effective remedial measures in many areas of public, employment and social life, including legal process.¹⁰¹ Zenker is chiefly concerned with conceptual clarification of ‘bias’ and ‘debiasing’, an essential—but too often neglected—precondition for successful experimental research in psychology or social science. Notably, this chapter takes a genuinely philosophical approach to foundational issues—reflecting Zenker’s own background and disciplinary affiliation—though ‘debiasing’ is not strictly a philosophical or jurisprudential term, but rather part of a broader, interdisciplinary project of theorising Evidence law. Unfortunately, the harvest, thus far,is meagre: ‘empirical research results are both scant and mixed … [and] may seem to deliver less than what one would have hoped for’.¹⁰² Zenker’s main conclusions are analytical rather than practical or reformist: ‘effective de-biasing measures must simultaneously address aspects of cognition, motivation, and technology, perhaps in ways more similar to personalized medicine than to a typical form of instruction. Being personally de-biasable, whatever this means, also presupposes a conducive institutional environment’.¹⁰³

Sandwiched between these sunny and darker sides of empirical psychology are two chapters engaging directly with evidence law and criminal process in the United States. Julia Simon-Kerr reconsiders ‘Relevance through a Feminist Lens’, starting from the question ‘what does it mean to apply “feminist” theory in the context of an evidentiary system designed by men?’¹⁰⁴ At least part of the answer to that question must contend with the thought that, insofar as evidence law is a product of historically evolved procedural traditions, it is doubtful whether anybody can be credited with its design.¹⁰⁵ This essay touches on significant issues and themes forced onto the law school agenda by feminist scholars and activists since the 1980s,¹⁰⁶ but many of them concern issues of substantive law with only derivatively evidentiary implications, as Simon-Kerr herself intermittently acknowledges.¹⁰⁷ If the applicable substantive law is sexist, this will inevitably skew evidential judgments of materiality and relevance, but it does not follow that the concept of relevance is itself discriminatory. In fact, what Simon-Kerr characterises as ‘theories of relevance’ are more properly culturally specific ‘common sense’ generalisations, some of which are indubitably still distorted by prejudice and bias,¹⁰⁸ and were even more brazenly disfigured within historical living memory. Normative legal standards infected by sexism, whether procedural or substantive, are in principle remediable through targeted law reform. More comprehensive feminist objectives to include formerly ‘silence[d] voices and narratives’ and ‘pivot the center’ in the ‘human struggle over which “social realities are better” or more real’¹⁰⁹ imply more radical social reform and cultural transformation, in which law would presumably be a supporting bit player; and evidence law, within that, a fleeting walk-on part. Generally speaking, the most obvious targets of institutional reform are litigation practice, such as the conduct of witness examination or the management of fact-finding, rather than evidence law as such. Besides, I doubt whether ‘rational logic’ or the Thayerite conception of relevance are in any way to blame for evidentiary practices that have ‘subtly or overtly privileged the perspective of white men to the exclusion of other voices’.¹¹⁰

In the book’s penultimate chapter, Jasmine Gonzales Rose investigates ‘Race, Evidence, and Epistemic Injustice’ by exploring ‘what makes racist evidence wrong as a matter of proof and truth’.¹¹¹ This is an intriguing question, since one might have assumed that racist evidence is self-evidently wrong because and for the same reasons that racism is wrong. Paralleling Simon-Kerr’s critique of gender bias, Gonzales Rose is concerned that ‘evidence rules, doctrines, practices, and policy rationales are employed or even more frequently overlooked to quiet, if not silence, the testimony, knowledge, and perspectives of people of color in the courtroom’.¹¹² Specifically, using previous convictions to impeach the accused’s testimony is racist because having criminal convictions ‘has become a racialized trait in the United States’;¹¹³ eyewitness identification is racist because, ‘due to white privilege, white witnesses’ identifications of suspects are more likely to be believed by jurors than witnesses of color even though white witnesses are statistically less reliable’;¹¹⁴ evidence of police violence is racist because prosecutors, grand juries and (white) trial judges refuse to credit or act on it; and evidence that a suspect evaded the police is racist owing to ‘the white norm that only the guilty flee … Under white racialized reality, police officers are protectors of the public and only guilty people would run from them’. The problem is compounded because, ‘Unlike white people who do not have knowledge about the relationship between people of color and police, many Black people have vast evidence-based knowledge of how police officers treat Black people’ and they know that ‘law enforcement should be avoided at all costs’.¹¹⁵ These strike me as sweeping (empirical) generalisations that highlight significant social issues but also raise as many theoretical questions as they answer. Gonzales Rose’s account would be more convincing if all the witnesses, police officers, judges and jurors in US criminal proceedings were white and all suspects and accused were Black: but that cannot be so. Like Simon-Kerr, Gonzales Rose tends to elide evidence doctrine, litigation process, inferential reasoning and fact-finding, but in a rather more totalising and reductive fashion. Her critique seems to amount to the proposition that, under ‘white racialized reality’, all judicial evidence is (potentially) racist, constituting distinctive forms of ‘epistemic injustice’.¹¹⁶ She does not say what, if anything, could be done to ameliorate the situation. Perhaps having Evidence students read, and discuss, her chapter would be a start?

Taking these two chapters as fair evaluation of contemporary US evidence law and legal process (I am patently unqualified to second-guess insiders), I am left wondering what, if any, more general (‘foundational’) lessons might be extrapolated from what are, on the face of it, intensely parochial discussions. Trait-based discrimination is surely likely to play out differently in different societies, cultures and legal systems. To what extent, for example, does the critique of ‘white privilege’ extend to societies where virtually everybody is white, or where almost nobody is? Are legal proceedings in Saudi Arabia dominated by ‘Arab racialised reality’, are those in Iran dominated by ‘Persian racialised reality’, in China by ‘Chinese racialised reality’, etc? Or is ‘racialised reality’ a meaningful concept only in a multicultural society? And if so, what follows for evidence law or Evidence law theory from that methodologically significant qualification? Is there any valid analogy between discrimination based on skin colour or ethnicity and forms of sectarian, sexual preference or disability discrimination? What about good old-fashioned class bias?¹¹⁷ The particularism of legal doctrine is especially prominent in these chapters. In English law, there is no ‘force or fraud’ requirement for rape,¹¹⁸ bad character evidence has never been restricted to non-propensity uses¹¹⁹ and previous convictions are no longer automatically admitted to credit.¹²⁰ Conversely, pre-trial silence—let alone ‘admissions by conduct’, such as trying to evade police pursuit and arrest—is routinely admissible in English criminal trials as a basis for adverse inferences,¹²¹ a practice that would be unconstitutional, and jurisprudentially scandalous, in the United States.¹²² Doctrinal details make a difference, even if they do not always show up in macroscopical snapshots of the bigger evidential picture.

Inasmuch as people are people, with similar cognitive capacities, affective attitudes and proclivities, everywhere on the planet, it is plausible to investigate, describe, critically evaluate and legislate for generic features of judicial evidence, proof and fact-finding that would be found in just about any modern legal system anywhere in the world. But this is a valid premiss only at a relatively high level of abstraction. Cognitive capacities and foibles shared by all human beings are inflected at the local level by contextual political, social and cultural factors, including—most pertinently for the present discussion—institutional features of legal processes that are highly variable, even as between jurisdictions that are geographically proximate, or even within a single territorial state. Sometimes, perhaps typically, local intersections between human cognition and institutional environments will be more interesting or consequential than universal capacities and generalisations. The implication is that Evidence theory needs to find productive ways, to engage with procedural traditions, institutional cultures and local jurisprudence to combine the generalities of human cognitive capacities and generic norms of social conflict resolution with the particularism of actual evidence law, in real-life legal proceedings, in existing legal systems. Comparative law offers extensive resources for this task,¹²³ largely untapped by Evidence scholars.¹²⁴

7. Concluding Criticism

Programmatic disciplinary (re)construction has a marketing dimension, as do the legal publications that are integral to it. PFoEL might have been titled ‘Theoretical Foundations of Evidence Law’ or simply ‘Evidence Law Theory’, but the virtues of literalism must be set against the opportunity to leverage disciplinary credibility through inclusion in a prestigious ‘philosophical foundations’ series. The book is impressive in its range of topics, contributor expertise and cosmopolitan authorship. Individual chapters should be widely read and used in Evidence law teaching wherever English is one language of instruction. The chapters are relatively short and incisive, most running to around 15 pages, which enhances their pedagogical value as accessible introductions and topical overviews, but limits their potential as original contributions to scholarship. Some of them reproduce in conspectus what their authors have argued at far greater length elsewhere.¹²⁵ There is something redolent of encyclopaedia entries to this format, though the generality of much of the content should ensure a reasonable measure of longevity for this edition.

The editors have performed sterling service in conceiving, organising and producing this volume, but their industry did not extend to providing readers with a metatheoretical roadmap to the disciplinary field they have seeded. This review has endeavoured to sketch in some of the missing contour lines, dramatic vistas and topographical features populating this terrain. My ‘jurisprudential’ version of the philosophical foundations of evidence law would have been no less interdisciplinary but more philosophical, more normative in multiple senses (legal and moral), more institutionally contextualised, less fascinated by theoretical puzzles, more interested in doctrinal materials and empirical realties. It would have extended the volume’s cosmopolitanism to include more regions of the world and different types of proceedings—including proceedings before international human rights courts¹²⁶ and international criminal tribunals.¹²⁷ It would have been less American, not in authorship necessarily, but in orientation and assumptions, not least because in many respects US evidence law is an unreliable representative of the extended common law family, exhibiting both positive and negative dimensions of US legal exceptionalism.¹²⁸ For a variety of interlocking reasons only gestured towards here, I favour a procedurally disaggregated model of evidence law conceptualised, in broader terms, as ‘criminal jurisprudence’.¹²⁹

Theoretical choices in disciplinary mapping are always informed by subjective preferences. Any critical appraisal of PFoEL ultimately stands or falls to the extent that it resonates with the experience, expectations, research agendas and pedagogical requirements of Evidence Law teachers, scholars and intellectually curious practitioners. Every critic is presumptively a lazy or frustrated author with an inflated view of their own talents. Those who believe they could produce a superior account of the philosophical foundations of evidence law now have, in this timely addition to our formative literature, an exemplary benchmark against which to prove it.