How Inadmissible Evidence Leads to Misjudging

By PON Staffon / Conflict Resolution

Adapted from “Think Twice Before You Go to Court” by Chris Guthrie for the April 2007 issue of the Negotiation newsletter.

Throughout the litigation process, judges gain new information at settlement conferences, motion hearings, discovery disputes, and the trial itself.

Inevitably, some of this information, though relevant to the case at hand, will be inadmissible under the rules of evidence.

Unfortunately, informational blinders can prevent judges from disregarding this information when making decisions.

To explore this phenomenon, DePaul University College of Law professor Stephan Landsman and Cleveland State University professor Richard Rakos gave a group of judges a hypothetical case in which a plaintiff, while attempting to burn leaves, suffered burns due to flashback from a gasoline container. He sued the manufacturer, claiming that the container was defective because it did not have a flame arrester to prevent flashbacks.

In defense, the manufacturer claimed that a flame arrester would not have prevented the injury. All the judges were asked to rule for either the plaintiff or the defendant based on this information. Another two groups of judges were also informed that the defendant had had to send a recall letter to consumers, warning them of the possibility of flashbacks from the containers.

Of these latter two groups, the first was told that another judge earlier had excluded the letter from evidence; the second was told that the evidence has been permitted.

All the judges who were not exposed to the information about the recall letter ruled in favor of the defendant, finding no liability.

Then there were two groups exposed to the recall letter. When the evidence was permitted, 25% ruled in favor of the plaintiff. Clearly, these judges were biased by the information even though it had been ruled inadmissible.

What does research suggest for litigants? It suggests that your trial outcome might be influenced by evidence that the law should not affect it.


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