If 'brainwashing' were the way that the government would deal with death-row, life sentence prisoners, what's to stop the government from using the same inhumane practices in other areas? :/
it's feasible to alter these people in a way that would allow them to become 'proper' citizens again, but that's dependent upon what is believed as a proper citizen, and such things are easily corrupted, despite whatever admirable intent there is.
That and I'll agree with Xia on the note that a lot of people that commit crimes do so in their 'right' mind, so putting them back into a right mind would probably be ineffective and just introduce a slew of more costly liabilities.
That's just me though. America could always do what Britain did, and just ship all their prisoners to some remote place (Australia) and let them fight it out with the locals and start their own country.