Every time there is a terrorist act or a mass murder, reporters start calling with questions on the psychiatric diagnosis of the perp. The default position seems to be that every religious extremist or political fanatic or mass murderer must be crazy. How else to account for their weird behavior?
Naming a diagnosis somehow satisfies a deep human need to explain what otherwise seems an unexplainable act. But names can only describe, they do not explain.
Our diagnostic system has chosen not to consider fanaticism a mental disorder. But confusion nonetheless arises because there is no clear boundary separating religious and political extremism from psychiatric illness. One man's cherished belief is another man's delusion.
Take a classic example that occurred at the birth of forensic psychiatry. In 1861, Charles Guiteau successfully assassinated President James Garfield -- based on the belief that he was God's messenger sent to the US to protect it from an evil administration. His trial created a sensation. More than a dozen expert witnesses divided down the middle on the question of his sanity. Guiteau's own words expressed the issue best: 'I would rather be hung as a man than acquitted as a fool."
The same scenario of adversarial expert testimony, for and against mental illness, has played out over and over again in trials of political and religious extremists (e.g., the Unabomber, Breivik, and some religious terrorists). Sincere fanatics detest the insanity defense because it invalidates their beliefs. They too would rather be punished as criminals.
Experts usually can't agree whether a political or religious criminal has done bad or is simply mad. Their canceling out suggests that the question is not really a medical decision, more a societal one. We must accept that there is inherent uncertainty in distinguishing the merely strange from the clinically insane. If we are to call Guiteau crazy for believing himself to be a messenger of God, how do we distinguish him from the many prophets and saints who have been so revered for making similar claims?
Jumping to a fake mental disorder diagnosis in everyone who is violent has another serious downside. It unfairly stigmatizes the mentally ill, most of whom are not violent. The public and the press must accept that political or religious violence is usually just political or religious, not very often the result of diagnosable mental illness.
This fits the wishes of most defendants. They would, like Guiteau, much prefer to be punished than treated -- lest their message be muffled. I would agree with them. Unless there is clear evidence of classic, pre-existing mental disorder, I would withhold diagnosis and give them the dignity of whatever is the suitable punishment.