"Beyond a Reasonable Doubt"—An Experimental Attempt at Quantification

Abstract

In American courts the burden of proof for determining guilt in criminal trials is the presentation of evidence which would lead "a reasonable man" to believe "beyond a reasonable doubt" that the defendant did indeed commit the act for which he was charged. This standard is applicable to all criminal acts irrespective of their heinousness or the circumstances under which they were committed. In instructing the jury, the judge explains his use of the phrase "beyond a reasonable doubt" by relying primarily upon paraphrases and by using what he believes are synonymous terms. Thus, a typical instruction sounds like this: Reasonable doubt is one a reasonable person has after carefully weighing all the testimony and is one a reasonable person would act or decline to act upon. It is not a capricious doubt or a fanciful doubt or a doubt arising in anyone's mind because of any sympathy for the defendant. It is in essence what the words obviously mean-a reasonable doubt. A reasonable doubt may arise not only from the evidence produced but also from a lack of evidence. The purpose of this research is to find out how subjects who are expected to apply that standard, namely, members of a jury, interpret its meaning, and to understand the relationship between the jurors' interpretation of the instruction and their verdict. From anecdotal evidence, it seems that the public translates the phrase "beyond a reasonable doubt" into "almost certain," "practically sure," "with only the slightest doubt"; or, if we were to restate the instruction in terms of a percentage or a probability, over a go per cent likelihood that the defendant committed the act for which he was charged. The findings reported in this paper describe one attempt at obtaining, if not a more accurate, at least a more easily communicated and a more reliable definition of the standard "beyond a reasonable doubt."