In every basic trial advocacy class I teach, I always read my students a snippet of jury selection advice from the renowned Clarence Darrow. At the time he authored this advice, it was “state-of-the-art.” However, as soon as I start reading it to them, my students will scoff, laugh, or gape in shock. Says Darrow, “The Englishman is not so good as an Irishman…The German is not so keen about individual rights except where they concern his own way of life…Beware of the Lutherans, especially the Scandinavians…” Darrow goes on and on like that, fumbling over all kinds of ethnic and religious stereotypes. It gives me the chance to remind my students how far we have come in ensuring the right to a trial by a jury of one’s peers, and to stop and think for a moment about where we need to go.
Thankfully, our laws continue to adjust against such prejudices in jury selection. Unlike Darrow’s time at the bar, modern jury selection tactics are increasingly backed by experimental science. Which brings me to an article Jules sent me recently which undertakes an experimental question on jury selection and a normative question about using peremptory strikes based on personality traits the attorney perceives. There is a lot of information in this article as it deals with the ethical, technical, and experimental. For brevity’s sake, I’ll confine this post to the latter—an age-old voir dire question of introverted jurors versus extraverted jurors, narrowly positioned around receptivity to expert opinions. The experiments here are quite detailed, so I’ll do my best to summarize them in such a short space.
The authors sought to discover what persuasive affects an expert with high or low credibility and high or low confidence had on introverted and extraverted jurors. The practical question should be clear here: If my case hangs on an expert or two, should I use peremptory strikes to craft a pool of introverted or extraverted jurors who tend to find an expert like mine more persuasive? Before we get to how the introverts and extraverts fared, it’s worth talking a bit about expert credibility and expert testimonial confidence as those terms are pregnant with meaning in these experiments and recur frequently below.
An expert can seem more or less credible for any number of reasons ranging from dress, to demeanor, to diplomas. As to their opinions, an expert can display varying degrees of caution or confidence. It is within these two categorical ranges that the experiments took place. The authors conducted two experiments. In the first, the authors did not change the projected testimonial confidence levels of the experts but they did in the second experiment, creating three categories of expert confidence: low, medium, and high. Participants watched an expert in psychology testify about the violence risk of a defendant convicted of capital murder then made a sentencing decision based on the expert’s recommendation.
Both introverts and extraverts were largely unmoved by low-credibility experts, even if the expert displayed high confidence. On the opposite side of the credibility spectrum, both introverts and extraverts were more likely to vote for the death penalty if the expert was high credibility and high confidence. None of that probably seems all that surprising to you. Here is where it gets interesting: Introverts were significantly more likely to vote for the death penalty with a high-credibility, low-confidence expert, whereas the high-credibility, low-confidence experts barely moved the needle for the extraverts. For the extraverts, a high-credibility, low-confidence expert was hardly more persuasive to them than the low-credibility experts who couldn’t seem to generate voting enthusiasm in either group. If an extravert thought an expert lacked confidence, they were more likely to also indicate that that expert lacked credibility. In fact, for the most extraverted jurors, a high-confidence, high-credibility expert produced a “multiplicative effect” on the chance of a death penalty vote. For the introverts, however, as long as the expert’s credibility was high, it did not matter if the expert’s testimonial confidence was low, medium, or high—they were more likely to vote for the death penalty and were even more likely to vote for it than their extraverted peers who saw their expert as both high credibility and high confidence.
You might want to read that last paragraph again. Speaking for myself, the repetitious terminology took a few swallows for me to properly digest. I don’t recommend spending any time at all in Darrow’s essay from 1936. You won’t even get it across your palate.
I have to give special thanks again to Nathan Wilson, a rising 3L at UNC and the Publications Editor of their law review, who has helped out three times now with my Bluebook citation formatting for this blog. I just hate doing them and Nathan has been such a cheerful helper, even though he isn’t my student.
 Clarence Darrow, Attorney for the Defense, Esquire, May, 1936 at 36 reprinted in James W. Jeans, Sr., Trial Advocacy 277-278 (2d ed. 1993).
 Erik J. Girvan et al., The Propriety of Peremptory Challenges for Perceived Personality Traits, 37 L. & Pysch. Rev. 49 (2013).
 I am simplifying the experimental procedures here for space. The authors employed a number of experimental devices and necessary controls, such as controlling for a participant’s opinion about the death penalty. Obviously, in order to determine a participant’s introversion or extraversion, each participant was tested and then categorized based on scientifically accepted criteria. See Id. at 63-65.
 Id. at 66.
 Id. at 66-67.
 Id. at 69.
 Id. at 70.