The general rule in Illinois is that evidence of other crimes is not admissible in a criminal jury trial because we fear that a jury may base its verdict, in part, on propensity. Put another way, we fear a jury may convict under the following train of thought: “If the defendant committed this crime once, he probably committed it again.” Propensity evidence is, indeed, often highly probative in the courtroom of common sense, but it is also highly restricted in a criminal jury trial because our system of criminal justice …