Paul Manafort trial, the jury asked the judge to define the term beyond a reasonable doubt (BRD). (Actually, jurors may have just asked about reasonable doubt, which indicates they were shifting their focus to the quality of doubt the defendant could produce, rather than focusing on whether the state proved guilt beyond a reasonable doubt. But that's a story for another day.) Of course, this has prompted much hand-wringing, including the usual claims from pontificating law professors and judges that there is no way to define BRD without creating further confusion.
But leaving BRD undefined is a huge problem. Studies that compare juror decision-making across the three burdens of proof -- preponderance, clear and convincing, and BRD -- demonstrate that jurors do not differentiate between / among the three standards. That is, in controlled studies, mock jurors' conviction rates are not affected by different burden of proof instructions.
Lawrence T. White and I just replicated those experiments, and found the same thing: when BRD is left undefined, the three burdens of proof do not produce significantly different conviction rates, all else being equal. Our study / article is currently under submission and we expect to finalize a publication agreement by the end of this week, so stay tuned for our pre-publication draft of our article, Is Reasonable Doubt Self-Defining? In the meantime, read my article in the Calif. L. Rev. Online for a proper definition of reasonable doubt -- one that puts the high burden of proof in context by comparing it to the lower, civil burdens of preponderance and clear and convincing.
But despite all of this, leaving BRD undefined is still better than what Wisconsin does. Wisconsin defines it in such a way as to completely demolish the burden of proof. As Larry White and I demonstrated in this Richmond study, and again in this Columbia study, Wisconsin's BRD instruction (JI 140) is so bad that it would be better for defendants if the term were not defined at all.