I'm sure most are aware of the microwave-generating crowd-control device that is was developed for the military. It may not end up being used on crowds or rioters, because of the severe pain it causes, but it would be a welcome addition to any torturer's toolkit. As long as it leaves no marks, the torturer can claim he never laid a finger on the victim.
If psychological trauma is allowed to be used as a coercion technique, it would only be a heavy incentive for torturer's to hide the damage their techniques inflict. Once the victim has been driven insane, he cannot testify against his torturer or plead innocent, and makes an excellent scapegoat. No one can prove he had ever been tortured at all, even if they could prove his innocence.