1 Wigmore on Evidence Section 7a (P. Tillers rev. 1983) (footnotes -- long footnotes -- omitted):
Several factors have a probable bearing on the judicial churlishness towards agreements to vary evidentiary rules. First, part of the explanation is surely attributable to changes in the general law of contract, which tend to restrict the scope of any party's ability to order his affairs through private contractual arrangements. Doctrines such as those relating to unconscionability and adhesion contracts have grown in importance in the last forty or fifty years. Wigmore's views as to the scope of freedom of contract are those of a late nineteenth and early twentieth century orthodox thinker. Recent developments in the law of contracts have eroded some of the premises that underlay his analysis of agreements to vary rules of evidence. But some of the judicial reticence to give full scope to agreements to vary evidentiary rules may reflect the fact that a great many of the decisions involve insurance contracts, and as we have remarked elsewhere (see note 10 supra), courts are particularly likely to construe insurance contracts against the insurer and otherwise place substantial limitations on the contractual freedom of insurance companies. To the extent that this factor dominates, the general implications of these decisions in regard to the validity and enforceability of agreements to vary evidentiary rules may be limited.
Second, and perhaps most important, we believe it is probable that many courts, notwithstanding the criticisms made by Wigmore, retain a vestigial sense that evidentiary rules are in some sense inappropriate "commodities" for bargaining between private parties and that in some sense rules of evidence involve fundamental aspects of justice that may not be bargained away. For our own part, we are not convinced that this view is wrong or that it is properly regarded as primitive and irrational. Rules of evidence have a special claim to our respect and attention since it is widely believed that their use, at least in the course of a jury trial, is necessary to maintain the reliability of the factfinding process. It is evident, of course, that the aim of reasonably accurate factfinding offers no ground for objection to agreements to vary evidentiary rules when those agreements do not undermine this objective and perhaps even further it by authorizing the admission of a wider range of evidence than would be normally admitted; after all, one may reasonably take the view, as many observers have (see § 37 infra), that a liberal attitude towards the admissibility of evidence is generally likely to promote accurate factfinding. (It is also possible, notwithstanding our conventional explanations, that many exclusionary rules do not in fact rest primarily on a concern for factual accuracy and truth. (See § 37.1 infra.) But of course any such agreements do not present the problem considered here. (Although, of course, there may be other reasons we might not wish to give effect, for example, to agreements that void the privilege against self-incrimination. See note 14 supra.) The problem we pose arises when we face agreements that authorize evidentiary practices and requirements that seem likely to make the judicial factfinding process substantially unreliable and arbitrary. A possible example here is the common attempt by insurers to require that proof of accidental death be evidenced by "visible contusions" or, less frequently, that the fact of death or injury be shown by "conclusive" evidence. If we believe that such evidentiary requirements promote arbitrariness and unreliability in judicial factfinding processes, is it any answer that the parties agreed that they should apply? We believe that a credible case can be made that the answer is no. And we believe that strong support for a negative answer is afforded by decisions that establish the principle that a court is neither required nor permitted to admit evidence that the court deems unreliable and worthless merely because the parties to the controversy have stipulated that such evidence shall be admitted.[fn35] Although we do not know whether God plays dice with the universe, a trial is not a crapshoot and the parties should not be permitted to demean the dignity and rationality of the judicial factfinding process merely because they agree to do so. It is one thing to say that a factual controversy shall not be submitted to a court for decision; it is another thing to say that the parties may force a court to resolve a factual controversy submitted to it for decision by methods that the court (and, perhaps, the public) regards as unreliable and arbitrary.
It is not self-evident that the limitation we believe should be imposed on the parties' ability to vary rules of evidence is consistent with the latitude that the law generally gives parties to make private arrangements for the disposition and adjudication of disputes that arise between them. After all, as Wigmore observed (see text supra), the law generally does permit parties to make agreements to arbitrate, and these agreements are today generally enforceable (see § 4e supra). Similarly, forum-selection clauses are generally enforceable, and these clauses, like arbitration submission agreements, permit the parties to bypass altogether the use of a particular system of judicial machinery. It may of course happen that a choice to bypass a particular forum is motivated by a desire to avoid the application of particular procedural and evidentiary rules that are applicable within a particular judicial system. In addition, the law generally permits parties to enter into stipulations by which selected factual issues involved in a controversy are eliminated. Finally, and perhaps most incongruously, the law generally allows lawyers to plead their clients into penitentiaries without the benefit of any formal adjudication of guilt or innocence.
We are not fully persuaded that all of these contractual rights are inconsistent with the denial of the right to parties to make agreements that destroy or significantly impair the reliability of factfinding in a judicial trial. Thus, for example, the choice of another forum, though it may avoid procedural and evidentiary matters that one of the parties finds undesirable, still involves the choice of a procedural system that has been deemed adequate by a societal judgment for the pursuit of truth, and the variations in evidentiary practices in different forums cannot be considered in isolation from the different procedural context in which those variations exist and operate. Nevertheless, not all procedural and evidentiary variations can be reconciled on this basis. Thus, for example, the ability of a party to make a plea bargain cannot be explained on this basis. And neither is it possible to reconcile in this fashion the right of parties to make arbitration agreements, for the parties to an arbitration proceeding generally have the right to adopt whatever procedural and evidentiary rules they please in the proceeding[fn36] (see § 4e supra). Nonetheless, these facts fall short of demonstrating that it is anomalous to deny parties the right to select whatever procedural and evidentiary rules they may please for use in a judicial trial. It is arguable that the proceedings in courts are not there solely for the convenience of the parties and that it is important for social reasons to maintain the solemnity and dignity of judicial proceedings regardless of the wishes of the parties. It is immaterial, in this view, that the parties have the ability to choose other types of adjudicative proceedings, such as arbitration, which they may structure in any fashion they deem appropriate. If pressed, we might concede that it is more difficult to explain away the form of plea bargaining proceedings since these proceedings ultimately do occur in the courtroom and the court does engage in certain limited findings of fact to assure itself that there is a "factual basis" for the plea entered. Driven to this point, we would not attempt to reconcile the irreconcilable; we would instead argue that plea bargaining proceedings are illegitimate creatures that should be driven from the courts of justice of our land and would further argue that in a criminal case every defendant should be given a trial that society deems sufficiently fair and adequate to ensure that facts are found reliably.