The study of one type of error—the conviction of innocent people—has gained enormous importance, attracting increasing academic research and indeed giving birth to an activism geared towards obtaining the exoneration of innocent victims of unjust court convictions. One of the issues that has produced the greatest number of studies has been identifying factors that increase the probability that convictions of innocent people will occur. Among its results is the consensus that a group of "evidentiary practices" exists that may explain the errors. The present work sets out to describe, from the evidence available, the most problematic evidentiary practices in relation to the use of expert evidence. According to the empirical data available, this is one of the most relevant factors in the system’s production of wrong decisions. Based on a more refined diagnosis of which practices are most problematic in the use of this evidence, I hope to make it possible to gauge the system’s weaknesses. This will allow me to develop proposals and strategies for risk prevention and minimization. Diminishing and anticipating errors not only seems a realistic goal or a reasonable aspiration, but also an imperative for the system

Forensic scientists are influential players in the justice system. At least two reasons may account for the great confidence placed in forensics. On the one hand, most people (and judges) have a rather poor science education, which leads them to place disproportionate expectations on the analysis produced by forensic science labs. On the other hand, DNA profiling has also contributed decisively to the prestige of forensic science. Unfortunately, there is no reason for such strong confidence, and experience shows that forensic science errors are also possible.

My argument is that it is impossible for a judge to both provide unrepresented and poorly qualified litigants with meaningful legal assistance while at the same time avoiding impartiality. The English system of civil justice offers poor access to litigants of limited means. This has been the case for a long time, but the problem has become even more serious since the abolition of legal aid in civil cases and there it is now urgent to address it. The strategy that seems to appeal to the legislator favours procedures that can be conducted without the involvement of professional advocates, of inquisitorial proceedings. This strategy is misconceived. While there is much to be said for simplifying the litigation system through use of technology, online resources and other labour-saving measures, there is no substitute for adversarial process.

If evidential legal reasoning is probabilistic, and rational certainty about a factual hypothesis is unattainable, then we need rules, called “standards of proof”, to determine the degree of probability required to be able to deem the assumption as proven. Only if we have standards of proof that indicate evidential thresholds will we be able to use other decision-making rules, such as burdens of proof or presumptions. Indeed, the purpose of burden of proof rules is to determine who loses the case if there is insufficient evidence of any of the hypotheses at issue. However, to apply these rules we need to know when the evidence is sufficient. The same is true of rebuttable presumptions, which require that a hypothesis be admitted in court (and used in the reasoning) in the absence of (sufficient) proof to the contrary. Therefore, for example, the presumption of innocence as a procedural rule means that defendants must be found innocent unless there is sufficient proof of their guilt. But when is the proof of a defendant’s guilt sufficient? Once again, implementing the presumption of innocence (like any other rebuttable presumption) presupposes the existence of a rule that establishes the evidentiary threshold.

As a number of modern sexual misconduct cases demonstrate, often there are multiple charges against a single individual under circumstances in which the proof of an individual charge may fall short of the required standard of proof, but in which it is clear – overwhelmingly, or beyond a reasonable doubt – that at least one of the charges is true, even if we cannot be sure which one. Building on earlier work by myself and Richard Zeckhauser, by Alon Harel and Ariel Porat, and by Ariel Porat and Eric Posner, among others, this paper, prepared for the World Congress on Evidential Reasoning at the University of Girona, offers a sympathetic examination of sanction imposition – inside and outside formal legal proceedings – on the basis of aggregate probabilities, and addresses a series of common objections. And the paper suggests that the greatest value of aggregating low (or lower) probability charges may be greatest outside the official judicial process. It also hints, albeit inconclusively, at the larger question of why the law focuses on acts when it is imposing sanctions rather than focusing on the actors who may have committed those acts.

In this study, I adopt an argumentative perspective on evidence, focusing on three points: (1) The structure of evidentiary inference; (2) which reasons count as good ones for establishing the degree of corroboration of a hypothesis and (3) the possibility of formulating a precise, objective standard of proof.

In chapter 3, I present the concept of “democratic dissonance,” which plays a significant role in the book. By this concept, I refer to the rupture between political practices and our expectations of them, a gap produced by institutions erected on the basis of assumptions about democracy and society that can no longer be sustained. In the chapter I maintain that the conception of democracy upon which the constitutional institutions were built was “restricted” (i.e., distrust towards majority rule and citizens’ participation in politics) and that the societies of those times were politically “contained” (i.e., in terms of restrictions on political rights). In this chapter, I suggest that such institutional legacy tends to create serious political problems when same institutions are directed to govern, in our time, a completely different social base, one marked by the conviction that public policies must be in line with our fundamental political claims and that our public life must be guided by our collective decisions.

The proposed constitutional organization of the political sphere, including, in a special way, the design of the executive and legislative branches, also reflected assumptions of democratic distrust. In this I explore the imbalance generated within the system of “checks and balances” by strong presidential systems and, in particular, by the presence of what some have called “hyper-presidentialism” (Nino 1997). In fact -I argue- the current system depends on finding a “President-angel” who is capable of and willing to demonstrate the qualities of her character throughout the term of her administration. When, on the contrary, the person elected President does not turn out to be up to the job, or is susceptible to pressure and influence, or takes offense at criticism from society and begins acting in an authoritarian or abusive manner, then the bare reality of the institutional system is revealed. And when this happens, we see that the system, in truth, is incapable of imposing firm control, that it allows abuse to continue, and that it is vulnerable to authoritarian manipulation. This situation -I maintain- should largely be seen as an endogenous product of the institutional system, much more than the result of personal pathologies (authoritarian leaders or unenlightened representatives).

In this chapter I examine the “real life” of dialogic constitutionalism. I begin the chapter by presenting the details of one recent dialogic example -namely the development of Argentina’s debate over abortion - and from that illustration I examine in which cases and for what reasons certain types of democratic dialogues may be considered valuable.

In this chapter (and following the conclusion of the previous one), I refer to the profound difficulties generated by legal interpretation, in general, and constitutional interpretation, in particular. I maintain that, very frequently -and particularly when constitutional values are involved- the words of the law offer some ambiguity or obscurity or vagueness - imprecisions that then must be resolved by the interpreter -typically, by a judge- applying the law to a particular case. The problem is that, unfortunately, interpretative methods-including, originalism, living constitutionalism, textualism, purposivism, strict constructivism- easily take the interpreters to opposite or very different solutions. In the chapter I show how this unfortunate situation strengthens the so-called “democratic objection”, in what relates judicial review; damages the main promises of the “rule of law”(because the “rule of man” rather than the impartial “rule of law” tends to prevail); and in the end favors authoritarianism and “democratic erosion” (thus, when abusive governments, recognizing how much the meaning of the law depends on the will of the interpreter, attempt to gain control over the judicial apparatus).

The question that I explore in this chapter is the following: what should delegates in a constitutional assembly do, in order to properly take into consideration the demands of rival groups, which are usually present in the context of multicultural, divided societies? In my analysis, I make reference to four different responses to the fact of pluralism, which we find in the history of constitutional conventions, namely “imposition,” “synthesis,” “silence” and “bundling”.After describing these four different responses, I concentrate my attention on the analysis of the latter –“bundling”- which has been the more significant and influential approach, within the history of constitutionalism in the Americas, and also one very important in other parts of the world..