Will Your Jurors Find Your Expert to be Knowledgeable and Trustworthy?
It's likely to depend on whether his or her opinion supports, ultimately, the values of each juror. And if the scientific consensus supports the expert's opinion it's likely to have less persuasive effect than you imagine. It's not a matter of your juror rejecting that consensus. Rather, it's a consequence of your juror assuming, perhaps because instances of agreement come readily to mind, that most experts actually support whatever conclusion about the issue would be deduced from that juror's values. That's my take anyway from the new paper (hat tip: The Situationist) "Cultural Cognition of Scientific Consensus" by Dan M. Kahan, Hank Jenkins-Smith and Donald Braman (part of the Cultural Cognition Project.)
At the conclusion of the paper the authors make a recommendation to those tasked with communicating risk that should be heeded equally by trial lawyers. "It is not enough to assure that scientifically sound information - including evidence of what scientists themselves believe - is widely disseminated: cultural cognition strongly motivates individuals - of all worldviews - to recognize such information as sound in a selective pattern that reinforces their cultural predispositions. To overcome this effect, risk communicators must attend to the cultural meaning as well as the scientific content of information". Swap "trial lawyers" for "risk communicators" and you'll get my point.
One last thing. I wonder what role reputation, and by that I mean the reputation of the subject and not that of the expert, plays in such matters. Here's why I ask. I know people who you'd predict from the authors' "hierarchical individualist" vs "egalitarian communitarian" distinction to fall into the "vaccines don't cause autism" camp instead being fervent anti-vaccination zealots. And I've found the reverse to be true as well. What actually seems most determinative is a like-minded group of friends. From my wholly unscientific observations some views about risk seem to spread among a group of friends or social acquaintances more like a virus. A new concern begins to be discussed, is seen as quirky, slowly spreads, then one day comes a tipping point and almost everyone in that group is announcing they won't be having their kids vaccinated (in the other group calls for the water-boarding of Jenny McCarthy are surprisingly typical) and the rest are feeling like Donald Sutherland in "Invasion of the Body Snatchers" (before the end anyway), and trying to change the subject.
