There are two articles dealing with this topic recently, or at least that I am aware of. One is a look at how incorrect brain functioning can contribute to criminality and the other is a criticism of a paper on free will. The take-home message is this: our actions are determined by the physical workings of our brains.
This causes a problem for free will in that it can’t be free. If we accept that our actions are determined by our brain and our brain functions according to physics and chemistry, the direction in which all evidence points, then we can’t really choose, at least we can only make one choice no matter how it feels to us. This is because everything that happens in our brain depends on the state it was in the moment before and so on. There is no way to make a choice that wasn’t already predetermined. In short there is no free will.
The lack of free will is also supported when you look at how the brain functions. Tumours or incorrectly-formed or damaged structures or injuries all affect how our brain processes information. If you remove or damage parts of the brain people will behave and think differently to how they did before. If someone does something bad it doesn’t mean that they were in the same situation as you when they did that, they had a brain that functioned differently (and different starting conditions and life experiences). Again it points to a lack of free will, or in this case at least a diminished value of free will as your brain’s structure is more important than your desires.
All this has implications for responsibility. How can you punish someone for something that they did not choose? In short how can you justify the idea of retributive justice? Simply, you can’t. But, as some might try to claim, this doesn’t mean people can just run around doing whatever they want without impunity. It does not mean that you have a world with no consequences for your actions, all it means is that why you punish someone must take the above into consideration. You can’t punish someone purely to punish them. What you must do is try for rehabilitation, where possible, or for a course of action that protects innocent people. You do not punish a murderer as revenge because he murdered people, you must punish him in order to protect other people from him. Before that, however, you must try to understand why he did what he did and how it can be prevented. If someone commits a crime for a neurological problem and it’s possible to fix the problem then you have accomplished something greater than just punishing them for what they did.