In theory, the Constitution protects us against criminal conviction unless the state can prove guilt beyond a reasonable doubt. In reality, this lofty standard is only as strong as the words used to explain it to the jury.
Unfortunately, attempts to explain reasonable doubt often create confusion, and sometimes even diminish the burden of proof. Many courts therefore believe that the better practice is not to attempt a definition. However, empirical studies demonstrate that reasonable doubt is not self-defining, i.e., when it is not explained to the jury, it offers defendants no greater protection against conviction than the two lower, civil burdens of proof.
To solve this dilemma, courts should explain reasonable doubt on a relative basis, within the context of the civil burdens of proof. A relative, context-based instruction will allow jurors to compare and contrast the different standards, thus giving them the necessary reference points to appreciate how high the state’s burden actually is.
This approach is rooted in a psychological principle called “contrast effects,” and is now supported by empirical evidence as well. In this Article, I present the results of my controlled experiment where mock jurors read the identical case summary of a criminal trial and were then randomly assigned to two groups, each of which received a different reasonable doubt instruction. The group that received the relative, context-based instruction acquitted at a rate 30 percent higher than the group that received a simple, undefined instruction. This result was significant at p < .05. Further, participants that received this relative, context-based instruction required a higher subjective confidence level in the defendant’s guilt before they were willing to convict.
Drawing on this and other behavioral research, this Article presents a comprehensive jury instruction on the presumption of innocence and burden of proof that is designed to fulfill the Constitution’s promise: to ensure that defendants remain free of conviction “except upon proof beyond a reasonable doubt.”