To me, off the top of my head, the criteria would be that the patient was suffering from a DSM-V-recognized severe mental disorder (this would be subject to statutory definition, but psychotic features would alone qualify), and demonstrating a stated intent to harm himself or another, or exhibiting threatening behavior. Jared Loughner and James Holmes would have qualified for this, as would my client and my sister. My sister, at age 14, was floridly mentally ill (though as far as I know she was not psychotic), and had threatened to kill my parents, me, and herself. The treating medical staff agreed it was appropriate to commit her and she was held for a full year.
I don't know if you saw this piece, but to me it provided a really interesting insight into the perspective of the parent of a violent, mentally ill kid:
http://www.huffingtonpost.com/2012/...er-mental-illness-conversation_n_2311009.html I think it is critical that people in this situation have realistic treatment options, potentially including long-term commitment, that are not predicated on a criminal conviction.