Morkus from Orkus
I'll bet it has been tried. I mean, The Men Who Stare at Goats was based on some amount of truth.Hypnosis... by trained therapists who (in many countries and states) are regulated by the government and is used typically with other types of therapy as well, not alone, on consenting patients ...and which may just be a placebo affect thing anyway, or a type of meditation. It's not movie-style mind control, since nobody can actually agree what hypnosis is or does anyway.
I can't find anything on using it to change the thoughts of the "criminally insane" anywhere, and I doubt it would work on anyone who wasn't willing to try--if it even works at all. Wikipedia lists hypnotherapy as an alternative medicine, along with crystals and phrenology.