In criminal law, diminished responsibility (or diminished capacity) is a potential defense by excuse by which defendants argue that although they broke the law, they should not be held fully criminally liable for doing so, as their mental functions were "diminished" or impaired. The defense's acceptance in American jurisdictions varies considerably. The majority of states have adopted it by statute or case decision, and a minority even recognise broader defenses such as 'irresistible impulse'. Some American states restrict the defense to the charge of murder only where a successful defense will result in a manslaughter conviction instead of murder. Until recently, the Republic of Ireland did not accept the partial defense. The Irish Supreme Court had rejected the existence of the defense in DPP v O'Mahony. The case was recently abrogated, however, by enactment of the Criminal Law (Insanity) Act 2006, effective June 1, 2006. The act, in pertinent part, specifically adopted the partial defense for the charge of murder where a successful defense will result in a manslaughter conviction instead of murder.