"An abnormal brain does not meant that the person cannot follow 
rules, although with certain very specific lesions it may. An 
abnormal brain also does not necessarily mean that the person is more 
violent. People who have acquired left frontal lobe lesions may act 
oddly, but their violence rate only increases from the base rate of 
3% to between 11% and 13%. a frontal lobe lesion in itself is not a 
predictor of violent behavior. In the case of an abnormal 
neurotransmitter disorder such as schizophrenia, there is a higher 
incidence of arrest for drug-related issues, but there is no higher 
incidence of violent behavior in people with schizophrenia while they 
are taking medication and only a very small increased incidence in 
those who are not. They still understand rules and obey them; for 
instance, they stop at traffic lights and pay cashiers. It is not 
true that just because you have schizophrenia, your base rate of 
violent behavior goes up and you are vastly more likely to commit a 
crime. If the court system concludes that having frontal lobe lesions 
or schizophrenia can exculpate a person for their behavior, that 
decision can result in two possible scenarios. Anyone with a frontal 
lobe lesion or schizophrenia has carte blanche for any behavior. Or, 
to take the opposite tack (which is based on the same reasoning that 
they cannot control their behavior), all people with frontal lobe 
lesions or schizophrenia should be locked up as a preventive measure, 
So in thinking about these things, we have to be careful that our 
best intentions aren't used inappropriately."

Gazzaniga et al, Cognitive Neuroscience, 2014, Norton, p 635

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