They also set standards for the psychiatrist in making judgments and serve as guideposts for the selection and use of observational data in making clinical inferences. They set limits of acceptable levels of confidence for opinion making and conceptualize the criteria for the degree of allowable risk of error in judgment formation. The application of these principles improves the probative quality of psychiatric evidence in both civil and criminal litigation. Although lawyers may welcome the exposition of these principles, they may also oppose their application in specific legal issues if one adversarial viewpoint appears to be favored. In cases such as civil commitment of mentally ill individuals or drug offenders, the standards tend to favor the defendant, because they require psychiatric material to show the causal relationship between the mental illness and legal standards for commitment. In contrast, in the issue of criminal responsibility of the mentally ill offender, the principles tend to favor the prosecution. Psychiatric opinion evidence is important for triers of fact, but guidelines for opinion making are crucial, given the nature of the data and the high risk of error in making psychiatric-legal opinions. Four references are listed.