The Principles of Judicial Proof: As Given by Logic Psychology and General Experience and Illustrated in Judicial Trials

The study of the principles of Evidence, for a lawyer, falls into two distinct parts. One is Proof in the general sense, — the part concerned with the ratiocinative process of contentious persuasion, — mind to mind, counsel to juror, each partisan seeking to move the mind of the tribunal. The other part is Admissibility, — the procedural rules devised by the law, and based on litigious experience and tradition, to guard the tribunal (particularly the jury) against erroneous persuasion. Hitherto, the latter has loomed largest in our formal studies, has, in fact, monopolized them ; while the former, virtually ignored, has been left to the chances of later acquisition, casual and empiric, in the course of practice. Here we have been wrong; and in two ways :

For one thing, there is, and there must be, a probative science the principles of proof — independent of the artificial rules of procedure hence, it can be and should be studied. This science, to be sure, may as yet be imperfectly formulated or even incapable of formulation. But all the more need is there to begin in earnest to investigate and develop it. Furthermore, this process of Proof is the more important of the two, — indeed, is the ultimate purpose in every judicial investigation. The procedural rules for admissibility are merely a preliminary aid to the main activity, viz. the persuasion of the tribunal's mind to a correct conclusion by safe materials. This main process is that for which the jury are there, and on which the counsel's duty is focused. Vital as it is, its principles surely demand study.

And, for another thing, the judicial rules of Admissibility are destined to lessen in relative importance during the next generation or later. Proof will assume the important place; and we must therefore prepare ourselves for this shifting of emphasis. We must seek to acquire a scientific understanding of the principles of what may be called “natural" proof, — the hitherto neglected process. If we do not do this, history will repeat itself, and we shall find ourselves in the present plight of Continental Europe. There, in the early 1800s the ancient worn-out numerical system of " legal proof " was abolished by fiat, and the so-called "free proof" — namely, no system at all was substituted. For centuries, lawyers and judges had evidenced and proved by the artificial numerical system ; they had no training in any other, no understanding of the living process of belief ; in consequence, when " legal proof " was abolished, they were unready, and judicial trials have been carried on for a century past by uncomprehended, unguided, and therefore unsafe mental processes. Only in recent times, under the influence of modern science, are they beginning
to develop a science of proof.