Evidence and Proof in Law

Recently, the practice of deciding legal cases on purely statistical evidence has been widely criticised. Many feel uncomfortable with finding someone guilty on the basis of bare probabilities, even though the chance of error might be stupendously small. This is an important issue: with the rise of DNA profiling, courts are increasingly faced with purely statistical evidence. A prominent line of argument—endorsed by Blome-Tillmann 2017; Smith 2018; and Littlejohn 2018—rejects the use of such evidence by appealing to epistemic norms that (...) apply to individual inquirers. My aim in this paper is to rehabilitate purely statistical evidence by arguing that, given the broader aims of legal systems, there are scenarios in which relying on such evidence is appropriate. Along the way I explain why popular arguments appealing to individual epistemic norms to reject legal reliance on bare statistics are unconvincing, by showing that courts and individuals face different epistemic predicaments (in short, individuals can hedge when confronted with statistical evidence, whilst legal tribunals cannot). I also correct some misconceptions about legal practice that have found their way into the recent literature. (shrink)

This paper defends an analysis of the epistemic contours of the interface between individuals and their cultural milieu.

This note discusses three issues that Allen and Pardo believe to be especially problematic for a probabilistic interpretation of standards of proof: (1) the subjectivity of probability assignments; (2) the conjunction paradox; and (3) the non-comparative nature of probabilistic standards. I offer a reading of probabilistic standards that avoids these criticisms.

A gunman intends to shoot and kill Victim. He shoots and misses his target, but the gunshot startles a group of water buffalo, causing them to trample the victim to death. The gunman brings about the intended effect, Victim’s death, but in a “deviant” way rather than the one planned. This paper argues that such causal structures, deviant causal chains, pose serious problems for several key legal concepts. -/- I show that deviant causal chains pose problems for the legal distinction (...) between attempts and completed crimes, and also for the distinction between attempts and mere preparations. I then suggest that cases of deviant causation undermine notions of legal liability for completed crimes in terms of actus reus and mens rea, and argue that natural accounts of negligence misclassify some cases involving deviant causal chains. After diagnosing several conceptual vulnerabilities in the law revealed by deviant causal chains, I show that natural strategies for shoring up legal theories in the face of these examples are unpromising. (shrink)

In 2001, three non-Aboriginal men in their twenties were charged with the sexual assault of a twelve year old Aboriginal girl in rural Saskatchewan. Legal proceedings lasted almost seven years and included two preliminary hearings, two jury trials, two retrials with juries, and appeals to the provincial appeal court and the Supreme Court of Canada. One accused was convicted. The case raises questions about the administration of justice in sexual assault cases in Saskatchewan. Based on observation and analysis of the (...) record, this paper: (1) examines relationships between legal errors dealing with availability of the defence of “belief in consent” and interpretation of the “all reasonable steps” provision, the need for retrials, and apprehended race-gender-age bias and discrimination; and 2) proposes incremental and systemic remedies to address the weaknesses in police, prosecutorial and judicial policy and practice highlighted by this case. (shrink)

This article examines the operation of “reasonable steps” as a statutory standard for analysis of the availability of the defence of belief in consent in sexual assault cases and concludes that application of section 273.2(b) of the Criminal Code, as presently worded, often undermines the legal validity and correctness of decisions about whether the accused acted with mens rea, a guilty, blameworthy state of mind. When the conduct of an accused who is alleged to have made a mistake about whether (...) a complainant communicated consent is assessed by the hybrid subjective-objective reasonableness standard prescribed by s. 273.2, many decision-makers rely on extra-legal criteria and assumptions grounded on their personal experience and opinion about what is reasonable. In the midst of debate over what the accused knew and what steps were “reasonable” given what the accused knew, the legal definition of consent in section 273.1 is easily over-looked and decision-makers focus on facts that are legally irrelevant and prejudice rational deliberation. -/- That is precisely what we see here; the result is often failure to enforce the law. The author proposes: -/- (a) that section 273.2 be amended to reflect the significant developments achieved in sexual consent jurisprudence since enactment of the provision in 1992; and -/- (b) that, in the interim, the judiciary act with resolve to make full and proper use of the statutory and common law tools that are presently available to determine whether the accused acted with mens rea in relation to the absence of sexual consent. (shrink)

In order to perform certain actions – such as incarcerating a person or revoking parental rights – the state must establish certain facts to a particular standard of proof. These standards – such as preponderance of evidence and beyond reasonable doubt – are often interpreted as likelihoods or epistemic confidences. Many theorists construe them numerically; beyond reasonable doubt, for example, is often construed as 90 to 95% confidence in the guilt of the defendant. -/- A family of influential cases suggests (...) standards of proof should not be interpreted numerically. These ‘proof paradoxes’ illustrate that purely statistical evidence can warrant high credence in a disputed fact without satisfying the relevant legal standard. In this essay I evaluate three influential attempts to explain why merely statistical evidence cannot satisfy legal standards. (shrink)

There is something puzzling about statistical evidence. One place this manifests is in the law, where courts are reluctant to base affirmative verdicts on evidence that is purely statistical, in spite of the fact that it is perfectly capable of meeting the standards of proof enshrined in legal doctrine. After surveying some proposed explanations for this, I shall outline a new approach – one that makes use of a notion of normalcy that is distinct from the idea of statistical frequency. (...) The puzzle is not, however, merely a legal one. Our unwillingness to base beliefs on statistical evidence is by no means limited to the courtroom, and is at odds with almost every general principle that epistemologists have proposed as to how we ought to manage our beliefs. (shrink)

The paper takes a closer look at the role of knowledge and evidence in legal theory. In particular, the paper examines a puzzle arising from the evidential standard Preponderance of the Evidence and its application in civil procedure. Legal scholars have argued since at least the 1940s that the rule of the Preponderance of the Evidence gives rise to a puzzle concerning the role of statistical evidence in judicial proceedings, sometimes referred to as the Problem of Bare Statistical Evidence. While (...) this puzzle has led to the development of a multitude of accounts and approaches in the legal literature, I argue here that the problem can be resolved fairly straightforwardly within a knowledge-first framework. (shrink)

Could it be right to convict and punish defendants using only statistical evidence? In this paper, I argue that it is not and explain why it would be wrong. This is difficult to do because there is a powerful argument for thinking that we should convict and punish defendants using statistical evidence. It looks as if the relevant cases are cases of decision under risk and it seems we know what we should do in such cases (i.e., maximize expected value). (...) Given some standard assumptions about the values at stake, the case for convicting and punishing using statistical evidence seems solid. In trying to show where this argument goes wrong, I shall argue (against Lockeans, reliabilists, and others) that beliefs supported only by statistical evidence are epistemically defective and (against Enoch, Fisher, and Spectre) that these epistemic considerations should matter to the law. To solve the puzzle about the role of statistical evidence in the law, we need to revise some commonly held assumptions about epistemic value and defend the relevance of epistemology to this practical question. (shrink)

Belief-state ascription — determining what someone “knew,” “believed,” was “aware of,” etc. — is central to many areas of law. In criminal law, the distinction between knowledge and recklessness, and the use of broad jury instructions concerning other belief states, presupposes a common and stable understanding of what those belief-state terms mean. But a wealth of empirical work at the intersection of philosophy and psychology — falling under the banner of “Experimental Epistemology” — reveals how laypeople’s understandings of mens rea (...) concepts differ systematically from what scholars, courts, and perhaps legislators, have assumed. -/- As implemented, mens rea concepts are much more context-dependent and normatively evaluative than the conventional wisdom suggests, even assuming that jurors are following jury instructions to the letter. As a result, there is less difference between knowledge and recklessness than is typically assumed; jurors consistently “over”-ascribe knowledge to criminal defendants; and concepts like “belief,” “awareness,” and “conscious disregard” mean different things in different contexts, resulting in mens rea findings systematically responsive to aspects of the case traditionally considered irrelevant to the meaning of those terms. -/- This Article provides the first systematic account of the factors driving jurors’ ascriptions of the specific belief states criminal law invokes. After surveying mens rea jury instructions, introducing the Experimental Epistemology literature to the legal literature on mens rea, and examining the implications of that literature for criminal law, this Article considers ways to begin bridging the surprisingly large gap between mens rea theory and practice. (shrink)

Mistakes are a fact of life, and the criminal law is sadly no exception to the rule. Wrongful convictions are rightfully abhorred, and false acquittals can likewise inspire outrage. In these cases, we implicitly draw a distinction between a court’s finding and a defendant’s actual guilt or innocence. These are intuitive concepts, but as this paper aims to show, contemporary use of the reasonable person standard in the law of self-defense muddles them. -/- Ordinarily, we can distinguish between a person's (...) material guilt or innocence and his juridical guilt or innocence. Someone is materially guilty if his actions in fact matched the conduct proscribed by the penal law. Someone is juridically guilty if he is found guilty by a tribunal, i.e., convicted by a judge or jury. When a tribunal convicts a innocent person or acquits a guilty person, the accuracy of its verdicts can be criticized. -/- There are three definitions of the reasonable person extant amongst courts and commentators: the reasonable person is either (1) a hypothetical ordinary, average person; (2) the embodiment of a community ideal; or (3) an embodiment of an objective ethical standard, i.e., ethical principles independent of community opinion. Nonetheless, after observing the circularity, vagueness, and lack of consistency in the definitions, wise courts and commentators have sometimes resorted to identifying the reasonable person with the judgment of the jury. -/- This piece argues that failure to settle on a fixed definition of the "reasonable person" in the criminal law of self-defense effectively conflates material guilt and innocence and juridical guilt and innocence at the doctrinal level. When courts do not clearly and consistently choose between standards one, two, and three, or when they expressly treat the reasonable person as a form of words standing in for the judgment of the jury, they make it conceptually impossible for observers outside the court system to apply a fixed, definite standard to assess the actual guilt of a person apart from the judgments of tribunals. -/- This paper's main purpose is to identify a conceptual knot rather than propose reforms. Still, it recommends two small changes meant to lift the confusion surrounding the reasonable person. First, it urges that courts expressly settle on one of the three definitions canvassed above. Second, it recommends that courts be mindful of the nature of the reasonable person standard and as such, be wary of treating conclusions about reasonableness as ordinary legal precedents, and wield the power of directed verdict aggressively to protect unpopular defendants from abuse by juries. (shrink)

This book explores a question central to philosophy--namely, what does it take for a belief to be justified or rational? According to a widespread view, whether one has justification for believing a proposition is determined by how probable that proposition is, given one's evidence. In this book this view is rejected and replaced with another: in order for one to have justification for believing a proposition, one's evidence must normically support it--roughly, one's evidence must make the falsity of that proposition (...) abnormal in the sense of calling for special, independent explanation. This conception of justification bears upon a range of topics in epistemology and beyond. Ultimately, this way of looking at justification guides us to a new, unfamiliar picture of how we should respond to our evidence and manage our own fallibility. This picture is developed here. (shrink)

This Article aims to demonstrate that the WTO jurisprudence on science-related trade disputes has become imbued with a specific vision of science that has prevented any possible application of the precautionary principle. This situation is due both to the WTO’s specific dispute settlement procedures and to the substantive nature of precautionary measures. Indeed, such measures’ foundation on “insufficient scientific evidence” dramatically undermines the probative value of science in WTO adjudication and creates a seeming contradiction: The system requires defendants to provide (...) legal evidence of the absence of sufficient scientific evidence. The reasoning of the Panel on the EC–Biotech case was riddled with this apparent paradox. For the first time, the US–Continued Suspension case has opened a gateway to address this fundamental issue. (shrink)

This exchange of correspondence with a critic provides helpful explanations of aspects of the paper "On Evidence, Medical and Legal" by the same authors.

The use of evidence to resolve uncertainties is key to many endeavours, most conspicuously science and law. Despite this, the logic of uncertainty is seldom taught explicitly, and often seems misunderstood. Traditional educational practice even fails to encourage students to identify uncertainty when they express knowledge, though mark schemes that reward the identification of reliable and uncertain responses have long been shown to encourage more insightful understanding. In our information-rich society the ability to identify uncertainty is often more important than (...) the possession of knowledge itself. In both science and law there are fundamentally different kinds of uncertainty at issue. There is uncertainty whether a particular hypothesis is correct, and there is uncertainty about observable data that may be generated if a particular hypothesis is correct. Both are expressed in terms of probabilities. Each has its own domain of application and its own logic, but the inter-relationship is complex and sometimes misunderstood. Hypothesis probabilities are always open to error through possible failure to take account of realistic alternatives, while the proper inferences that can be drawn from data probabilities (often in the context of significance testing) are quite limited and easily over-interpreted. When considering these two kinds of probability in a court of law it is possible to interpret the phrase 'reasonable doubt' in different ways. It can be seen as addressing data uncertainty: whether such incriminating evidence might with reasonable probability arise to confront an innocent person. Or (the more conventional view) it can be seen as some sort of threshold level on the probability that the defendant is guilty (a hypothesis probability). Each typically involves elements of subjective judgement, but fewer issues and uncertainties arise when considering the data probability and it is argued that this is often the more critical and proper issue for a jury to address. This has particular repercussions for cases involving identification of a suspect through trawl of a DNA or other database. (shrink)

This book examines the legal and moral theory behind the law of evidence and proof, arguing that only by exploring the nature of responsibility in fact-finding can the role and purpose of much of the law be fully understood. Ho argues that the court must not only find the truth to do justice, it must do justice in finding the truth.