My family member has work experience with people who deemed insane after they pleaded insanity. Two were placed in a psychiatric facility on a high acuity unit with limited to none security measures as it ain’t no prison pardon my double negative. One was prosecuted for murders, the other don’t know what for.

One ran away from psych hospital the same day he was placed there by law enforcement and was on a loose for two weeks. It was all over our newspapers, he was eventually caught. No idea where he went as obviously he didn’t return to the same hospital. The other one ran away eventually too and killed someone on outside the same day.

So in summary in my experience people who plead insanity defense and deemed too insane to serve their sentence are pretty much out there on the loose. Psychiatric facilities they are placed to aren’t equipped to keep them there as they are not prisons plus restraint (except certain extreme circumstances) is prohibited

Even high acuity units in psychiatric hospitals absolutely aren’t prisons and personnel aren’t prison guards. These are medical faculties, not jails

Yes prison and jails are not mental institution. But mental institutions cannot ensure that people will actually stay there as those aren’t prisons.