Diminished capacity: a moral and legal conundrum

The diminished capacity doctrine allows a mentally abnormal but legally sane defendant to have his or her mental abnormality taken into account in assessing criminal liability.’ Depending on the jurisdiction, diminished capacity operates either to negate an element of the crime charged, thereby exonerating the defendant of that charge, or formally to reduce the degree of crime for which the defendant may be convicted and punished even if all the formal elements of the originally charged offense were satisfied. These two variants of diminished capacity will be referred to respectively as the “mens rea” and “partial responsibility” approaches.’ This contribution will analyze the theoretical basis and development of diminished capacity doctrine with special reference to the law in the State of California, where the doctrine is especially fully, if not coherently, developed. I shall contend that although the doctrine appears to express intuitively held notions about moral and legal responsibility, it is neither morally necessary nor socially desirable. In the alternative, it will be claimed that if moral intuitions