The massacre in Tucson has provoked a lot of punditry and finger-pointing; Glenn Reynolds and Jack Shafer and Ross Douthat have adequately refuted the stupidity and shamelessness of blaming "political discourse," (Loughner appears to have taken his ideas from a conspiracy theorist "David-Wynn: Miller," who believes the extra hyphen and colon in his name protects him from government mind control, and has held a grudge against Giffords since 2007) so let me turn to a separate and more important issue.
Loughner was widely viewed by those who interacted with him even only briefly as unstable, mentally ill, and dangerous—dangerous enough that Pima Community College hired lawyers and must have felt it was risking a lawsuit to get him off campus. An armchair psychologist would quickly diagnose schizophrenia. How can society protect itself against the psychotic?
The question is a tough one that requires balancing of interests: if it's too easy to institutionalize and forcibly medicate someone involuntarily, there are obvious liberty implications reminiscent of the Soviet Union's hospitalizing political prisoners. But waiting until a schizophrenic actually shoots up Virginia Tech or a Tucson parking lot before incapacitating them has obvious public safety issues. And any policy will be enforced by fallible human beings who will make mistakes: no matter where you set the public policy, you will have false negatives that could have been avoided by more aggressive intervention or false positives that could have been avoided by a government more solicitous of liberty interests. It's a serious debate to be had and, ironically, Congresswoman Giffords was apparently one who took issues of mental illness seriously.
Ten years ago today, a person with untreated mental illness shot and killed 19-year-old Laura Wilcox and two others. My rule of thumb is a strong presumption that any law named after a victim is poor public policy enacted by legislators who confuse voting against a law with voting against an innocent person, and I'm therefore skeptical of "Laura's Law" in California, which "authorizes court-ordered treatment for individuals with severe mental illness who meet specific legal criteria." But I admit ignorance where exactly the balance should be struck.
On that question, in the wake of the Virginia Tech shootings, Sally Satel wrote persuasively in the Weekly Standard in 2006 that public policy has shifted too far away from the public-safety balance because of threats of litigation from a federal government agency that you probably have never heard of, the Substance Abuse and Mental Health Services Administration, which is part of HHS, and from state agencies funded by the federal government. SAMHSA activism has precluded "Laura's Law" from being executed in more than two of California's 58 counties.