Not as smart as we think we are…

An interesting study in the Journal of Empirical Legal Studies on juror assessments of negative evidence in criminal trials has revealed that most of us are aren’t great at making complex probability calculations.

Hardly surprising, as psychological researchers and behavioural economists have been telling us for decades that humans tend to default to crude heuristics when faced with complex problems.

In ‘Evaluating Negative Forensic Evidence: When Do Jurors Treat Absence of Evidence as Evidence of Absence?’ William C. Thompson, Nicholas Scurich, Rachel Dioso-Villa and Brenda Velazquez reminded us of how important it is to keep this fact in mind in the context of jury trials.

The study demonstrated that when faced with negative evidence (meaning evidence of things that were not found, such as missing fingerprints, absence of gunshot residue etc), jurors are not always able to appropriately weigh the probative value of such findings. Specifically, the study demonstrated a “poor calibration between probability of detection and the weight given to negative evidence.”

This finding has important implications for the presentation of negative evidence in jury trials. More research is needed to find out how this evidence can be presented in a way enables fact-finders to give it the weight it deserves.

Read the study here: