Judging Demeanor

This Article challenges the conventional wisdom that defendant demeanor—affect, body language, and physical appearance—helps juries assess guilt. On the contrary, we show that demeanor evidence poses an inherent risk of propensity-based reasoning. It invites jurors to convict defendants based on whether they “look like criminals,” rather than on the actual facts of the case. In doing so, demeanor evidence facilitates cultural and racial subordination. It enables members of dominant groups—consciously or not—to penalize members of less-dominant groups for failing to appear innocent or credible. We argue that existing law has things backwards. It treats defendant demeanor as presumptively useful and puts the onus on defendants to demonstrate prejudice. The proper approach, by contrast, would treat defendant demeanor as presumptively prejudicial and require the state to develop case-specific theories of probative value. This would give trial courts the tools they need to properly instruct juries and to regulate prosecutors, and it would revitalize the role of appellate courts in safeguarding trial fairness. Furthermore, it would integrate demeanor with other types of evidence, such as a defendant’s criminal history or sartorial presentation, already identified in the case law as inherently risky. We conclude by offering a number of concrete proposals to implement this change, including a new model rule of evidence (“Rule 404(c)”), restyled jury instructions, and ideas for reform beyond the courtroom.