在刑事诉讼法里，精神障碍防御（英语：Insanity defense，即以精神障碍为理由的辩护）是可行的。被告提出：因为在他们进行被指控的犯罪活动时精神障碍，他们不应该因触犯法律而承担相关的司法责任。

有人声称因精神障碍而免于或减少刑事处罚至少可追溯到汉谟拉比法典。从不同视角看精神障碍辩护都有其可取之处：一些人认为它是状态辩护，一些人认为它与缺少蓄意相关，还有些人认为它不过就是一个借口。这里涉及到的精神障碍有不同的法学定义但非医学术语：譬如有南顿规则。

The insanity defense, also known as the mental disorder defense, is a defense by excuse in criminal trials arguing that the defendant is not responsible for their actions due to an episodic or persistent psychiatric illness. Exemption from full criminal punishment on such grounds dates back to at least the Code of Hammurabi. Legal definitions of insanity or mental disorder are varied, and include the M'Naghten Rules, the Durham rule, the American Legal Institute definition, and other provisions, often relating to a lack of mens rea ("guilty mind"). In the criminal laws of Australia and Canada, statutory legislation enshrines the M'Naghten Rules, with the terms defence of mental disorder, defence of mental illness or not criminally responsible by reason of mental disorder employed.