The idea that "If determinism is true, then no one is responsible for anything" doesn't have to be true: a person acting criminally is still the most proximal cause of the bad behavior and should be held accountable; the Big Bang isn't to blame for his criminality. Moreover, by this reasoning, everyone who commits crimes is not responsible because their brains made them do it: if determinism is true, they also had no choice but to 'sin'. So why should a seemingly healthy offender go to jail (where he doesn't get rehabilitated and doesn't learn to not repeat his offenses), while one with a brain tumor or schizophrenia should be treated medically and perhaps even reinstated into society?
The celebrated cognitive neuroscientist Michael Gazzaniga has a new book coming soon, Who's In Charge - about the implications of neuroscientific findings for the law. To promote it, Slate printed an excerpt that asks what it means for responsibility and culpability if free will doesn't exist.
These questions, I think, lead us think of determinism and free will as inappropriate for the legal system. If no one has a choice in their behavior, then clinically sick people shouldn't be treated any differently from anyone else; if no one is responsible for their actions, then sick people aren't somehow "less responsible" than others.
What emerges is that those who "can't help" but to act criminally (i.e. the schizophrenics) are treated medically and released back into society when they're healthy again (psychiatry has a whole lot of catching up to do if that is to actually happen; perhaps neuroscience can help?). So why don't we also treat those criminals who appear healthy? If their brain made them kill, then there must be something wrong with it. What I'm driving at is that a judicial system based on retribution doesn't make much sense. Wouldn't we be far better off if we actually fixed criminals? Perhaps that's wishful. Or worse, dystopian.