“The devil is in the details,” he said of New York’s new law. “The two fears are that people will be deterred from seeking treatment that they need or that, once they are in treatment, they will clam up and not talk about violence.”

Most mental health experts agree that the link between mental illness and violence is not imaginary. Studies suggest that people with an untreated severe mental illness are more likely to be violent, especially when drug or alcohol abuse is involved. And many rampage killers have some type of serious mental disorder: James E. Holmes, accused of opening fire in a movie theater in Colorado in July, was seeing a psychiatrist who became alarmed about his behavior; Jared L. Loughner, who killed 6 people and injured 13 others in Arizona, including former Representative Gabrielle Giffords, was severely mentally ill.

But such killings account for only a tiny fraction of gun homicides in the United States, mental health experts point out. Besides the research indicating that little violent crime can be linked to perpetrators who are mentally ill, studies show that those crimes are far more likely to involve battery — punching another person, for example — than weapons, which account for only 2 percent of violent crimes committed by the mentally ill.

Because of this, some criminal justice experts say it makes more sense to pass laws addressing behavior, rather than a diagnosis of mental illness. In Indiana, for example, firearms can be confiscated from people deemed a potential threat, whether or not they have a mental illness.

Proposals in a number of states seek to redefine the threshold for involuntary commitment to psychiatric treatment. But in doing so, they have reignited a longstanding debate about the role of forced treatment.

In Ohio, lawmakers are expected to consider a proposal to increase access to outpatient commitment instead of hospitalization, while also doing away with language requiring people with mental illness to show a “grave and imminent risk to substantial rights” of themselves or others before they can be committed.

In Colorado, where legislators are undertaking a broad overhaul of the state’s mental health system proposed by Gov. John W. Hickenlooper, a Democrat, the proposal also includes changing the criteria for involuntary commitment.