Right from Wrong in the Justice System

Neuroscience - Law - The Brain on the Stand - Jeffrey Rosen - New York Times: "American law holds people criminally responsible unless they act under duress (with a gun pointed at the head, for example) or if they suffer from a serious defect in rationality — like not being able to tell right from wrong. But if you suffer from such a serious defect, the law generally doesn’t care why — whether it’s an unhappy childhood or an arachnoid cyst or both. To suggest that criminals could be excused because their brains made them do it seems to imply that anyone whose brain isn’t functioning properly could be absolved of responsibility. "

As we begin to understand the brain better, we will begin to understand that our actions are not entirely under conscious control. How do we determine what we can control and what we can't? Can a brain cyst or a chemical dependency which overpowers our decision-making processes be used to absolve us of responsibility?