Dateline: September, 2010, Issue 2

How well do jurors understand jury instructions on reasonable doubt?

Reasonable doubt instructions are the cornerstone of decision-making in criminal cases, and possibly the most important instruction provided to jurors.

Ellsworth (1989) found that jurors were very clear on the notion that they had to be convinced "beyond a reasonable doubt" but, at the same time, none of the jurors were able to define what reasonable doubt meant.

Kramer and Koening (1990) compared reasonable doubt understanding for jurors who had served jury duty and those who had been called but had never served.

Only 25% of jurors in both groups thought they should return a not guilty verdict if they had any reasonable doubt.

Further, 68% of the instructed jurors thought that reasonable doubt could only be based on evidence, and not conclusions drawn from the evidence, whereas only 52% of uninstructed jurors made this mistake.

In sum, jurors do not understand reasonable doubt jury instructions particularly well, and the instructions can lead jurors to make mistakes.

Source Ellsworth, P. (1989). Are twelve heads better than one? Law and Contemporary Problems, 52, pp. 205-224.

Source Kramer, G., & Koening, D. (1990). Do jurors understand criminal jury instructions? Analyzing the results of the Michigan juror comprehension project. University of Michigan Journal of Law Reform, 23, pp. 401-437.