As difficult as such matters are to disentangle after the fact, it is even harder to say ahead of time which deluded malcontents will become cold-blooded murderers. In retrospect, every strange thing Loughner did or said marked him as a dangerous madman, including not just overtly crazy stuff like his video linking Pima Community College to genocide, but borderline behavior such as singing to himself, talking out of turn, pestering teachers about grades, smiling and laughing inappropriately, and making weird comments in class. But it is not hard to see why administrators and police officers might have considered him a nuisance rather than a menace.
Even among people diagnosed as schizophrenics, Torrey says, only 10 percent become violent. So assuming that Loughner qualifies for that label, a policy of detaining people with similar symptoms would sweep up nine harmless individuals for each future criminal.
Although they are routinely called upon to say whether people pose a danger to themselves or others, psychiatrists are notoriously bad at it. "Over 30 years of commentary, judicial opinion and scientific review argue that predictions of danger lack scientific rigor," notes University of Georgia law professor Alexander Scherr in a 2003 Hastings Law Journal article. "Scientific studies indicate that some predictions do little better than chance or lay speculation, and even the best predictions leave substantial room for error about individual cases. The sharpest critique finds that mental health professionals perform no better than chance at predicting violence, and perhaps perform even worse."
The current system of involuntary commitment rests on predictions of dangerousness that are appallingly inaccurate. Abolishing the requirement of dangerousness would avoid that embarrassment at the cost of imprisoning even more people who pose no threat to others.