PBS has streaming video and a careful analysis of the case of Eric Michael Clark, who at 17 and while mentally ill, shot and killed a police officer in Arizona. His case is currently the basis for a Supreme Court review of the insanity defence in US law.
Clark had reportedly been diagnosed with paranoid schizophrenia and was psychotic at the time of the offence, and was under the delusion that his town was being controlled by aliens.
Before the Supreme Court, Clark’s lawyers argued that the insanity defence is so difficult to prove in his home state of Arizona as to make it unjust.
The criteria for the insanity defence varies wildly among US states, with some not allowing the plea, some following the M’Naghten rules and others having a more strict version.
The M’Naghten rules state that for a person to be sane (and therefore responsible), they must be aware that such an act is wrong, and that they were aware of the “nature and quality of the act” at the time.
If it can be established that mental illness had impaired either of these two conditions, the person can be declared legally insane.
However, Arizona only has the first of these conditions as the test for insanity. So even if a person is not aware of the nature of the act they are committing – if they have an abstract understanding that this act would be wrong – they can be held legally responsible for the act.
In Clark’s case, his lawyers are arguing that although he knew killing a police officer was wrong, he believed the person to be an alien, and so was not able to apply his understanding to the situation owing to his mental impairment.
If the Supreme Court agree that Arizona’s criteria for the insanity defence is unjust, other states might have to implement the M’Naghten rules.
If they rule that Arizona’s criteria are adequate, other states may adopt this more strict criteria and reject the M’Naghten rules.