The basic rule limiting character evidence is quite sensible. Personality traits predict less than most people (including jurors) realize; situations, and person-by-situation interactions, are more potent forces. As the law suspects, people tend to perceive the behavior of others through lenses of propensity; consequently, they over-attribute and over-predict consistency between character and conduct. In fashioning the character evidence rules, common law judges correctly diagnosed a problem and took steps to temper those attributional tendencies to avoid inaccurate and unfair verdicts. The rules allow numerous exceptions, admitting some character evidence out of fairness or to permit helpful evidence while barring its most misleading variants. For example, defendants in criminal cases are permitted to offer evidence of their own character or the character of a victim. Other exceptions are made to assist factfinders to evaluate witness credibility. A special class of that rule deals with witnesses’ criminal records: a maze of sub-rules governs admissibility of prior crimes. Research finds that people tend to rely on prior crime evidence for its improper propensity purpose, contrary to judicial instructions about the limited use to which it may be put. A relatively new set of rules permits prior criminal sexual conduct to be admitted, allowing factfinders to draw inferences about “any matter to which it is relevant.” These rules are controversial because they invite jurors to engage in the very propensity thinking that centuries of evidence doctrine prohibited. Moreover, behavioral data do not support the theory behind a special rule for prior criminal sexual conduct.