Pro-gun advocates may think they can steer the national conversation away from the semiautomatic rifle used to kill 20 Connecticut first-graders by bringing up their killer's reported mental instability.

But they're wrong.

For the first time in decades, there seems to be real momentum to further restrict the purchase and possession of firearms. President Obama seems genuinely committed, and politicians who pledge allegiance to the National Rifle Association in return for generous contributions to their war chests sound open to change.

That said, mental illness must be part of the discussion of how to prevent another massacre like the killings at Sandy Hook Elementary School. Even as authorities admit they don't know why Adam Lanza shot 20 schoolkids and six teachers, his mental state rises to the top of their list.

Lanza shot his mother to death before heading to the school, and killed himself as police stormed the building. He was said to have Asperger's syndrome, but that mild form of autism isn't being blamed for his violent tendencies, which reportedly had Nancy Lanza thinking about having her son committed to an institution.

The possibility that Lanza suffered from depression or some other mental illness suggests a tragedy might have been prevented had he received adequate treatment. It's possible. The same goes for countless individuals with mental disabilities who could lead more fulfilling lives if they were receiving proper care.

But providing that care isn't always easy. First of all, the public doesn't view mental illness the way it does other diseases, so mental health agencies struggle to receive adequate support. Secondly, since most of the mentally ill do better outside institutions, there is a greater chance that some who have been prescribed medications won't take them.

The dilemma of how to make sure the mentally ill receive proper treatment, either in an institution or as an outpatient, while not trampling on their constitutional rights to refuse treatment has never been answered satisfactorily. You don't stop being an American citizen because you're sick.

In fact, Mental Health America, the nation's largest mental health nonprofit, says, "Given that only a tiny fraction of violent acts are perpetrated by persons with mental health conditions, efforts to bar such individuals from purchasing firearms or to increase preventive detention can have no meaningful impact on public safety."

While MHA acknowledges a risk of violence by some "individuals who have an untreated or undertreated substance use disorder," it believes "involuntary mental health treatment is a serious curtailment of liberty." It says the mentally ill in most instances shouldn't be involuntarily committed or forced to take medication.

In the aftermath of the Sandy Hook shootings, people want to live in an America better equipped to intercede before a potential mass murderer starts killing children. Both the MHA and NRA are saying care must be taken not to arbitrarily take away anyone's constitutional rights. That may make reaching the goal of a safer society harder, but not impossible.