The disease post contains the following especially relevant argument:
So here, at last, is a rule for which diseases we offer sympathy, and which we offer condemnation: if giving condemnation instead of sympathy decreases the incidence of the disease enough to be worth the hurt feelings, condemn; otherwise, sympathize.… Yelling at a cancer patient, shouting “How dare you allow your cells to divide in an uncontrolled manner like this; is that the way your mother raised you??!” will probably make the patient feel pretty awful, but it’s not going to cure the cancer. Telling a lazy person “Get up and do some work, you worthless bum,” very well might cure the laziness. The cancer is a biological condition immune to social influences; the laziness is a biological condition susceptible to social influences, so we try to socially influence the laziness and not the cancer.
Translating this into the terms of crime by people with brain tumors: does knowing that they will go to prison if they commit the crimes their tumors are making them commit affect their decision? If people with brain tumors commit just as many crimes in countries where they will be imprisoned as in countries where they could make a successful insanity defense, then the punishment doesn’t work as deterrence and should be dropped.
The disease post contains the following especially relevant argument:
Translating this into the terms of crime by people with brain tumors: does knowing that they will go to prison if they commit the crimes their tumors are making them commit affect their decision? If people with brain tumors commit just as many crimes in countries where they will be imprisoned as in countries where they could make a successful insanity defense, then the punishment doesn’t work as deterrence and should be dropped.