The problem is, nobody knows what that means. Or I should say, "mental illness" carries no meaning which can contribute to security against random violence by future Jared Loughners.
There is no viable anti-violence strategy in the field or profession of mental health.
There is supposed to be such a strategy, but it doesn't exist. The public presumes if somebody's crazy, and they hurt or threaten other people, then they get treated so they'll be less violent.
The trouble is, this "treatment" is highly unreliable. It makes some people more violent.
All one need do is observe a well-contested trial where psychiatric expert opinion is deemed relevant. Any side can pay their psychiatric whores for the court, but the pretense of medical science would only be laughable if it weren't so terrifying.
Illinois paid hundreds of thousands of tax dollars to convince juries that C. Rodney Yoder was a ticking time bomb and absolutely had to be imprisoned in the Chester nuthouse for life to protect the community. They were wrong. Yoder refused all treatment, got out, and has been a productive citizen.
A Chicago judge recently let a murderer found not guilty by reason of insanity go free without any psychotropic meds. Half a dozen psychiatrists testified in unanimous agreement, and the murdered victim's mother was in court to see her daughter's killer released.
Bottom line? Mental illness means nothing.
Jared Loughner took aim with his Glock 9mm at a nine-year-old girl he'd never seen before, and he pulled the damned trigger. That was horrifying, crazy, evil, inhuman. But it wasn't caused by an illness, and it won't be an issue for medicine. It'll be an issue for justice.
A jury of ordinary people will decide what to do with Loughner, not a doctor. And if the jury sentences him to death, they should draw straws for who flips the switch to kill him.
True believers condemn politicians for exploitation and think more "treatment" is the answer to the Tucson tragedy. They probably think a machine carries out a death sentence, too.
Those who've been in the nuthouse know not to whistle past the graveyard.