Evidence Law as a System of Incentives

• Author: John Leubsdorf
• Position: Professor of Law, Rutgers School of Law-Newark
• Pages: 1621-1662

My thanks to Dale Nance and William Stuntz, whose writings helped give rise to the thoughts expressed here, to the participants in a Cardozo Law School colloquium, and to Bernard Bell and Jon Hyman.

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Evidentiary rules are often appraised from the viewpoint of a judge who must decide whether to admit evidence at trial. From this perspective, the judge should admit relevant evidence unless its contribution to a correct decision is outweighed by the likelihood that it will seduce the trier of fact to decide on improper grounds, by its harm to extrinsic policies such as those underlying the evidentiary privileges, or by its imposition of excessive cost or waste of time. Needless to say, current law does not limit itself to such ad hoc balancing, but deploys, with questionable rationality, a complex structure of rules.¹ Nevertheless, in applying or criticizing those rules we still often put ourselves in the shoes of a judge asking John Maguire’s classic question: “Shall we let it in?”²

The discussion here starts from a different question: Will adopting this rule encourage or discourage parties from seeking and presenting evidence that the trier of fact should consider? In other words, this Article will appraise Evidence law ex ante, as it shapes parties’ incentives up to the moment when evidence is presented and objected to, rather than ex post, as it governs rulings on the objection. This means that evidentiary rules must be considered from the perspective of parties and advocates as well as from that of a judge. Although other scholars have started this discussion,³ many instances of incentives and disincentives in Evidence law remain unexplored and unsystematized.

My goal here is to contribute to an ex ante rethinking of Evidence law which—as when one views a landscape through ultraviolet binoculars—will reveal it in an unfamiliar and instructive light. Seen in this way, Evidence law may lose its familiar appearance as a plane demarcated by linear boundaries, assuming instead the appearance of a space suffused by fields of force pulling in various directions.

This Article considers a variety of incentives and disincentives to the introduction of evidence. Part I briefly appraises the incentives created by the adversary system, showing that these incentives fall short of ensuring the optimal presentation of evidence. Part II continues the discussion by analyzing the Best Evidence Principle and the ways in which it encourages the presentation of evidence and in which it too falls short. Part III discusses three different ways in which incentives provided by Evidence law can affect the quantity and quality of evidence. Incentives can encourage or discourage the creation of evidence, they can encourage or discourage its presentationPage 1624 in court, and they can encourage or discourage forgery and spoliation of evidence. Next, Part IV reviews some objections to the approach pursued here, especially the claim that Evidence law should seek to influence primary behavior in the real world, not just the creation and presentation of evidence in adjudicative proceedings. The Article concludes that lawmakers, lawyers, and scholars should be more alert to the ways in which rules of evidence reach forward to help shape peoples’ behavior in preparing for and conducting disputes.

I Adversariness and Its Limits

Adversary incentives provide a familiar and powerful, but ultimately incomplete, justification for entrusting the presentation of evidence to the parties rather than to the courts. Each litigant has motives to search out and introduce all evidence that might help persuade the trier of fact while shunning evidence that an opponent with similar incentives will be able to demolish. Rules excluding evidence can impede the operation of these incentives and, ever since Jeremy Bentham, reformers have urged that courts should not keep evidence from juries on the ground that it is inferior or may be overvalued. Reformers argue that we should rely on the adversary system and the jury’s common sense to give evidence the weight it deserves. Carried to its logical conclusion, this implies that courts should exclude evidence only when its reception wastes time and money or inflicts collateral harm such as invasion of privacy or harassment of witnesses.

Although even radical reformers in the United States have not been willing to go this far,⁴ many reforms adopted in the nineteenth and twentieth centuries depend on adversary incentives to seek and sift evidence. Two obvious examples of reliance on the parties to find and introduce evidence that they deem valuable are repealing rules that disqualified many witnesses from testifying⁵ and liberalizing the hearsay rule.⁶ Beyond the scope of Evidence law, broadening discovery in civil cases⁷—and to some extent criminal cases⁸—and recognizing a Constitutional right to effectivePage 1625 assistance of counsel in criminal cases⁹ reflect a similar reliance on adversary incentives.

So why do we need multiple rules curtailing the admissibility of evidence rather than one rule allowing each party to introduce all relevant evidence?¹⁰ Six sets of replies show why adversary incentives are ultimately inadequate.

First, bringing relevant evidence before the trier of fact is not the judicial system’s only goal. Rather, the system also seeks goals that the parties cannot always be relied on to vindicate. For example, privilege rules seek to encourage certain confidential relationships and to protect those who enter them.¹¹ Privileges thus exist under judicial systems, like the German one, which place few restrictions on the admissibility of evidence.¹² Other rules encourage post-incident remedial measures, settlement, and related activities.¹³ Similarly, some exclusionary rules seek to deter improper police conduct.¹⁴ We will return later to such extrinsic goals.¹⁵ Adversary incentives alone do not vindicate all these other goals, and therefore require supplementation.

Second, the judicial system must be concerned with cost in addition to completeness. This concern is vindicated by rules allowing the judge to exclude needlessly cumulative or time-consuming evidence.¹⁶ Adversary incentives will not control costs. Of course, parties consider the costs they themselves bear, but they do not internalize the costs that their use of evidence imposes on other parties, or its costs and benefits for the legal system. Indeed, parties may seek to increase an opponent’s costs in order to coerce a settlement.¹⁷ Evidence rules provide some slight protection against such efforts to escalate costs, though a serious effort to force internalizationPage 1626 would require much more—or something quite different, such as cost-shifting rules.

Just as adversary incentives fail to control external costs, they fail to account for external benefits. Rules requiring litigants to use more expensive evidence or risk losing the case¹⁸ might reflect a conclusion that the public benefits of an accurate decision exceed the costs to the parties.¹⁹ But identifying instances of party underinvestment would require lots of unavailable information, and exclusionary rules would usually be a clumsy and ineffective way to cure them. In short, cost considerations warrant qualifications to relying on the parties to find and introduce relevant evidence unhampered by evidentiary rules, but in our present judicial system, these qualifications are usually marginal ones.

Third, limiting the parties’ freedom of proof can be justified by endemic inequalities in the adversary system.²⁰ Sometimes, one party has greater access than the other to decisive evidence. The availability of discovery tends to equalize the parties in this respect, but not always.²¹ A party with more money and more at stake can often out-investigate, out-discover, out-conceal, and out-introduce its opponents.²² And even two wealthy and motivated parties will not always enjoy representation of equal caliber. When such inequalities predominate within an identifiable class of cases, the inequalities can justify rules requiring the advantaged party to produce witnesses whose statements it proposes to use²³ or to carry a burden ofPage 1627 coming forward with evidence.²⁴ Likewise, Federal Rule of Evidence 801(d)(2)(D) reflects the reality that employers have greater access to their own employees’ testimony than their opponents do. It therefore allows an employers’ opponent to use employees’ statements, when they were made during their employment and are about a matter within their employment’s scope, against the employer.²⁵ More dramatically, the requirement of proof beyond a reasonable doubt in criminal cases tends to extract from the government the evidence that it has greater resources than most defendants to obtain—though it also encourages defendants to withhold their own evidence.

In principle, courts could also modify adversary incentives to remedy inequality in a particular case—for example, when one party is wealthier than the other. Some jurors may indeed consider the parties’ wealth when appraising the absence of better evidence, but I know of no authority justifying this approach, much less incorporating it into procedural or evidence law. Many would consider it to violate the principle that a litigant’s wealth should not...