The Preponderance of the Evidence Suggests Jurors Create Their Own Burden of Proof

O.J. Simpson was found liable for the deaths of Nicole Brown Simpson and Ron Goldman by all the jurors in the civil case, but for at least one of them, the instructions to make her finding based on the burden “a preponderance of the evidence” were not not followed.  Instead, for her to find Simpson “guilty,” as she said on TV following the trial, she needed to believe it “beyond a shadow of a doubt.”

The blurring of the lines between the two Simpson cases is somewhat understandable, yet clearly “beyond a shadow of doubt” is beyond the burden of proof even in a criminal case.  Given the results of that trial, it’s easy to overlook a juror who manufactured here own burden of proof, but what if it had gone the other way?  Would juror misconduct charges have been pursued, or even discussed?  Would a mistrial have been declared, or, instead, would there have been just a collective shrug?

Is it even possible to get jurors to adhere to a burden of  proof?  Are the instructions clear if they are not also persuasive?

I recently conducted a jury research project in a civil case in Los Angeles.  As usual, prior to the plaintiff and defense presentations, I gave the jurors an explanation of the burden of proof in a civil case.  I used the “scales of justice” explanation, where I explained the plaintiff must tip the scales at least slightly in its favor.  I also used the “51%” explanation, as well as the one that incorporates the “more likely than not” language.  In short, I gave the instructions on the burden of proof every way I have heard it given in court and, following the defense presentation and prior to the jurors answering their verdict question, I reminded the respondents of the burden.

The questionnaire that followed the case presentations was quite lengthy, 132 questions, the last one of which was as follows:

Q132.  A plaintiff in a civil case must prove its claims by a “preponderance of the evidence.”  Write the number that represents the level of certainty you required of the plaintiff in this case.  _____%

At least two factors should be considered in connection with the responses to that questions.  One is a fair criticism that my “jurors” probably did not know with certainty what level of proof they actually required of the plaintiff in this study.  That said, “certainty” is not always the goal, and answers to that question did at least represent a reflection of their states of mind, so it had validity in that respect.  The validity is increased by the fact that the question included a reminder of the burden, earlier explained as the “51%” rule.  So, even if their answers did not reflect the level of proof they required for their verdicts, it was at least a test of whether they remembered the instruction and how they felt about it.

Secondly, one might suggest that since this was a “mock trial,” the stakes were not real, so the responses may not reflect the burden of proof those same respondents would have adhered to had they been sitting as jurors in the actual case.  On the whole, this is not a valid position.  If it was, the validity of jury research itself would be equally in doubt, and that question was answered in the affirmative long ago and many times over since.

With that, consider the data from Q132 from 33 mock jurors.  The number in parenthesis is the number of respondents who wrote the % number in the blank space provided.

0% (1), 45% (1), 49% (2), 50% (1), 51% (9), 55% (1), 60% (1), 65% (1), 68% (1), 70% (1), 75% (5), 80% (5), 85% (1), 90% (1), 100% (2)

Considering the instructions given to the group, it is not surprising that 51% would appear as the mode (the answer most frequently chosen), but in light of the emphasis placed on the explanations of the burden, what a weak mode it was.  More than half entered a number higher than 51%, in and of itself not an entirely unreasonable position, but the vast majority of those were at 75% or higher.  Two people converted “a preponderance of the evidence” into the “100% rule” (a.k.a. “beyond a shadow of doubt”) while the respondent who wrote “0%” was probably just mocking the question itself and should be ignored.

Keep in mind, I provided the mock jurors with three typical plain-language explanations.  If anything, it was a more complete explanation than provided by most judges.  Those respondents also answered Q132 in relatively close proximity to receiving the instructions and the question itself included a reminder of the language of the burden.

So, how can those results be explained?  Is the language used to describe the burden inadequate?  At least in this instance, that does not seem reasonable.  Are the results in my research project a variation on the so-called “C.S.I effect?”  Are jurors so accustomed to the burden of proof in a criminal case they cannot, or will not, adopt a different rule for a civil case?  I suggest instead that jurors, like people in general, resist being told how to think, how to weigh evidence, or what number to assign to “more likely than not.”

I invite you to weigh in on this issue and I look forward to your comments.  Please do so in the form of comments to this posting in LinkedIn (if that is how you learned of it), or via emails to me (, as, due to a high volume of spam, I have had to delete the “comments” feature on this website.

I also invite you to read the other articles posted in this portion of the website and to check out my new book, Fixing the Engine of Justice:  Diagnosis and Repair of Our Jury System.

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