It would change nothing. We incarcerate to deter crime, and deterrents are a factor in decisions regardless of if you believe free will is a meaningful concept.
> Some people are still gonna have to be locked up
The point is not that people do not need to be deterred, but that the nature of that deterrence and the policies related to locking people up must change with such a revelation.
Such a revelation would also explain rates of recidivism, and shine a light on how counterproductive our current policies most likely are.
As we learn more about the brain, some form of this is already playing out. Accused criminals have been exhonerated on account of tumors growing on their brains, the removal of which returned the individual to “normal”.
Tumors are obvious, but as we learn more, I suspect we’ll find that many forms of criminality may be treatable.
This is as preventative, restorative and rehabilitative as it could ever be?