By Dr. Ken Broda-Bahm:
The witness is in good shape and the testimony looks to be great. There's just one little problem in his past: a conviction. Litigators are understandably concerned about any threats to witness credibility, but if that threat comes in the form of a rap sheet, that's viewed as a very damaging fact, if not a ticking time bomb. The effects of a prior conviction are most often written about in a criminal defense context where the research generally shows that the fact of a prior conviction significantly increases the chances of a current conviction, particularly where the prior conviction is for a similar crime. But it can be a factor for any witness who's had a prior brush with the law. In civil cases, crimes involving dishonesty can be admitted for the narrow purpose of impeaching a witness's credibility. A recent study (Stanchi & Bowen, 2014) that focused on a civil trial context looks at the question of whether the damage is as bad as one might suspect. The results? No it isn't. In a realistic controlled study, the researchers found that prior conviction evidence did not increase the chances for an adverse verdict. Instead, emphasis on the conviction caused mock jurors to frame the trial as more of a zero sum contest on witness credibility -- a frame that can end up actually benefiting the convicted witness.
These results have some implications for attorneys assessing the risks to their witnesses' credibility. Those risks can factor heavily into case assessment and strategic choices, with attorneys sometimes making an extreme effort to keep prior convictions out, or keeping their witnesses off the stand in order to limit this evidence. If the effect of prior convictions is not as damning as attorneys assume, then some of these cures could be worse than the disease. This post looks at the new study and shares some practical implications for those who are considering the effects of a prior conviction on either their own witness or the other side's witness.