Study 1 analyzes questions asked by actual deliberating jurors in order to identify sources of juror misunderstanding in criminal pattern jury instructions. Instructions concerning 'reasonable doubt,' criminal 'intent,' the use of evidence concerning prior convictions, and the general duties of jurors, are selected for further investigation. Study 2 uses videotaped trial materials to pinpoint linguistic problems that confuse jurors and interfere with their abilities to accurately comprehend and apply the selected pattern jury instructions. Available knowledge concerning psycholinguistics is then applied to rewrite the troublesome instructions; in addition, legal expertise is consulted to help assure that the rewritten instructions are legally valid. Study 3 demonstrates that the rewritten instructions improve jurors' understanding relative to Pattern or No instructions. Overall, the research indicates the availability to the criminal justice system of improved methods for instructing jurors accurately and effectively in the law. (Publisher abstract)