By Dr. Ken Broda-Bahm:
Consider the expert witness mismatch: One expert represents the common mainstream scientific view, while the other expert is there to support a theory that lies on the far side of the credibility spectrum, and may have just barely survived a Daubert challenge. Yet what jurors see is an equivalency. One expert is on one side, and one is on the other. The views of wackier expert may represent 1 percent or less of the relevant scientific community, but in the courtroom, that expert rises to 50 percent of what is shared. The comedian John Oliver noted this problem in a recent segment of HBO’s Last Week Tonight. Suggesting that the media set up a false parity when pitting one scientist who believes in man-made climate-change against one scientist who discounts it, Oliver’s solution is to represent the true proportions. So he invites three climate-change skeptics to share their views, and then fills the studio with ninety-seven scientists on the other side.
Of course, that solution isn’t available to litigators. In court, that effort to represent the proportional weight of opinion would be shot down faster than the other side can say "cumulative." The general problem is referred to as the fallacy of “false equivalency,” and this democratic notion that there are always “two sides to the story” can end up giving an unearned advantage to a side that is far less reflective of consensus and evidence. Various conspiracy theories benefit from that treatment, as do more mainstream topics such as the perceived health risks of immunizations. In these public discussions as well as in the courtroom, there needs to be a way to cut through the false equivalency and emphasize what is more fully supported based on the weight of evidence and expert opinion.