Keeping people locked up serves three purposes, 1) Rehabilitation, 2) Deterrence, and 3) Social-protection (although some would argue for "Punishment", and still others would argue for Justice (vengeance)).
The bottom line is that criminals keep doing stuff that the rest of us don't like and we want them to stop. The first two speak to that end, and the third is the last resort of keeping them the hell away from us forcibly. Realistically, this very notion is at odds with our founding principles of Liberty and self-direction, making it difficult to really and truly change the criminal to suit us.
This leads to the "brain-wipe" postulate. We can simply stop dicking around with expensive counselling, job training, and education programs and simply reprogram their brains, burning out the bad stuff in the process. In each scenario, we are forcibly making the criminal change to suit us. Save time and just give him a program we can live with.
Well, lots of good doctors and researchers have hit on a potential brain-wipe technology, transcranial magnetic stimulation, where magnetic fields tweak the operation of their nervous system. (No, I don't think the unit looks like the "neural neutralizer" gizmo used on Kirk in this Star Trek episode, but that'd be cool.)
But we still need to be able to verify that said criminal is actually repentant (or properly reprogrammed). Big problem without mind reading technology.
Interestingly enough, two news stories are out last week that address that very issue! The first was a team of researchers using fMRI: 'Thoughts read' via brain scans, which was pretty cool in itself -- mapping the brain then using a MRI to figure out what circuits were firing, again using very strong magnetic fields. Heck, a smart engineer ought to be able to combine both the mind-wipe and the mind-reading functions into an integrated unit, saving the prison budget millions.
Then, in a magical moment of serendipity, I read that the Brain Region Tied to Regret Identified.
Wonders just plain never cease. When the parolee goes before the parole board, he can just be hooked up to one of these to see if he really is sorry, or is just putting on an act to get out of jail to do evil onto others again. Science comes to the rescue and takes all the guesswork out of soft, mushy human second-guessing procedures.
Or alternately, the mindwipe/reprogramming machine can just look in the right region to see if he's a "new man".
Way cool. Coming to a prosecutor's office near you (I know this because I really doubt that I'm the only person pulling this data together into an effective convict management program.)