From that NYT piece:

Perhaps more significant, we are not very good at predicting who is likely to be dangerous in the future. According to Dr. Michael Stone, professor of clinical psychiatry at Columbia and an expert on mass murderers, “Most of these killers are young men who are not floridly psychotic. They tend to be paranoid loners who hold a grudge and are full of rage.”

Even though we know from large-scale epidemiologic studies like the E.C.A. study that a young psychotic male who is intoxicated with alcohol and has a history of involuntary commitment is at a high risk of violence, most individuals who fit this profile are harmless.

Jeffery Swanson, a professor of psychiatry at Duke University and a leading expert in the epidemiology of violence, said in an e-mail, “Can we reliably predict violence? ‘No’ is the short answer. Psychiatrists, using clinical judgment, are not much better than chance at predicting which individual patients will do something violent and which will not.”

It would be even harder to predict a mass shooting, Dr. Swanson said, “You can profile the perpetrators after the fact and you’ll get a description of troubled young men, which also matches the description of thousands of other troubled young men who would never do something like this.”

Even if clinicians could predict violence perfectly, keeping guns from people with mental illness is easier said than done. Nearly five years after Congress enacted the National Instant Criminal Background Check System, only about half of the states have submitted more than a tiny proportion of their mental health records.

How effective are laws that prohibit people with mental illness from obtaining guns? According to Dr. Swanson’s recent research, these measures may prevent some violent crime. But, he added, “there are a lot of people who are undeterred by these laws.”

This is a phony, phony, phony issue when it comes to gun crime in America.

All the focus on the small number of people with mental illness who are violent serves to make us feel safer by displacing and limiting the threat of violence to a small, well-defined group. But the sad and frightening truth is that the vast majority of homicides are carried out by outwardly normal people in the grip of all too ordinary human aggression to whom we provide nearly unfettered access to deadly force.

Richard Friedman M.D. is saying pretty much the exact same thing I wrote a couple of days ago:

ICYMI: The pro-gun lobby is pushing this talking point hard, but don’t fall for the ‘mental health’ diversion lgf.bz/UUc9QE

— Charles Johnson (@Green_Footballs) December 19, 2012