Juries are asked to consider whether a defendant committed a particular act; they’re not supposed to decide cases based on evidence suggesting a tendency to commit such acts. ‘Propensity’ evidence—which indicates that a defendant has done similar things on other occasions—is therefore usually inadmissible. ¶ So the jury wouldn’t hear about a shooting by [Chicago police officer Marco] Proano two years after he killed Niko Husband—a shooting that was captured on video. …. ¶ The rule about propensity evidence also applies to alleged victims, so the jury wouldn’t hear about Niko’s criminal record either.
Steve Bogira, “Can a lawsuit deliver justice after a fatal police shooting?”