Standards of proof define the degree to which jurors must be satisfied that a fact is true, and plaintiffs in civil lawsuits assume the burden of proving their claims to the requisite standard of proof. Three standards—preponderance of evidence, clear and convincing evidence, and beyond a reasonable doubt—are used by different jurisdictions in trials involving liability for punitive damages. We investigated whether individual mock jurors apply these standards appropriately by instructing them to read two personal injury trial summaries and to use one of three standards in either qualitative or quantitative format when deciding punitive liability. Results showed that jurors tended not to incorporate the standard into their judgments: defendants were just as likely to be found liable when the plaintiff's burden was high (“beyond a reasonable doubt”) as when the burden was low (“preponderance of evidence”). The format of the instruction also had a negligible effect. We suggest that nonuse of the standard of proof is related to jurors' preferences for less effortful or experiential processing in situations involving complicated or ambiguous material. Copyright © 2012 John Wiley & Sons, Ltd.