DENVER — A year after a Colorado inmate held in solitary confinement allegedly gunned down the state prisons chief upon being released, lawmakers are moving to restrict use of the punishment for the mentally ill.

The bill continues the efforts that Colorado Department of Corrections Director Tom Clements had been working on, and highlights a growing movement by states to limit the practice of solitary confinement amid questions about its effectiveness.

Lawmakers in a House committee Tuesday unanimously approved the measure, which would forbid placing inmates in solitary confinement if they have a serious mental illness, unless there are pressing circumstances. The bill already has cleared the Senate.

“I think it’s absolutely needed for public safety,” said Democratic Rep. Joe Salazar, who is co-sponsoring the proposal. In recent years, legislators have raised concerns that inmates who are released directly to communities after spending long sentences in solitary confinement pose a greater threat to society.

Amy Fettig, senior staff counsel at the American Civil Liberties Union national prison project, said state legislative activity trying to limit the use of solitary confinement, or study its effectiveness, has increased recently — a recognition that mentally ill inmates who act out sometimes can’t control their behavior.

“And that sometimes instead of punishing them, they really need treatment,” Fettig said.

In 2007, New York passed legislation to limit putting mentally ill inmates in solitary confinement, and other states have since taken a closer look at the practice, Fettig said. Maine and New Mexico are working to reduce the overall number of inmates placed in solitary confinement after passing legislation to study the issue, she said. Nevada and Texas also passed study bills last year, according to Fettig.

Bills to reduce the overall use of solitary confinement are pending this year in New York, California and Massachusetts, but the debate on the issue is much broader.

“A conversation is going on in virtually every jurisdiction in this country — and for good reason,” Fettig said.

The mental health effects of being placed in solitary received more attention in Colorado after Clements’ death. The lone suspect, Evan Ebel, was a former inmate who had been released after serving eight years in prison, much of it in solitary confinement.

“The tragedy of (Clements’) death was an example of why the policy wasn’t working,” said Democratic Sen. Jessie Ulibarri, who carried the solitary confinement bill in the Senate. “We were warehousing people with serious mental health issues in long-term isolated confinement, then we were dropping them off back in the community with no transition back to human contact, no mental health care, and it’s incredibly dangerous.”

Before his death, Clements had been trying to limit the use of solitary confinement, and prison officials have continued his work.

Rick Raemisch, Colorado’s new corrections chief, told lawmakers in December that there were only eight mentally ill inmates in solitary confinement, compared with 140 the year before. As of Tuesday, there was only one mentally ill inmate in solitary confinement, according to the department.

To try to better understand what inmates go through, Raemisch himself spent 20 hours in solitary confinement, which he said left him “feeling twitchy and paranoid.” He wrote about his experience in an opinion letter to the New York Times in February.