the-psychology-of-expert-credibilityLitigation is a battle. The American system of jurisprudence is based upon the adversarial system: two sides confront each other, examine and cross examine expert witnesses and lay witnesses, and take their best shot at convincing a jury, or a judge, that the facts and the law are on their side.


While attorneys often have to convince the jury why their expert witness is better than their adversary’s expert witness, how does an attorney explain to the jury why two seemingly honest and fair minded lay witnesses, having seen the same event, came to completely different conclusions?

It’s not always beneficial to accuse your adversary’s witness of being untruthful; particularly when they actually believe what they’re saying. Yet you still have to undermine their credibility. How do you go about walking that fine line?

Have an expert witness psychologist explain that some witnesses’ testimony is more equal than others.

In an illuminating article from the journal Applied Cognitive Psychology, entitled “Estimating the effects of misleading information on witness accuracy: can experts tell jurors something they don’t already know,” psychologist authors McAuliff and Kovera explain that inaccuracy need not always be explained by bias.

Specifically, a witness’s accuracy (not honesty), is statistically influenced by their age. According to the study, the likelihood and the extent to which lay witnesses are “suggestible” (defined as the “effects of misleading information on witness accuracy”), decreases with age. In other words, experience counts.

The implications are readily apparent: if your witness is older than your adversary’s witness (presumably not too old – but that was not measured in this particular study), you may increase the likelihood of convincing a jury that he/she is more reliable by having a psychologist explain this phenomenon as an expert witness.

In this “game of inches,” a jury’s decision could well turn on the smallest of suggestions that the “elder statesman” witness is more reliable.

By: Ian Heller, J.D.