AUGUSTA, Maine — Robert King knows isolation.

For nearly 30 years, King spent 23 hours of every day locked up in a small, windowless cell in Louisiana’s infamous Angola Prison for a crime he did not commit.

Speaking during a recent visit to Maine’s State House, King said the hope of one day proving his innocence and gaining release helped him maintain some shred of sanity.

But for many others in long-term solitary confinement, the isolation is mind-bending — even tortuous, he said.

“If someone is a danger to himself or others, they need treatment. They need to be isolated,” said King, who was released from Angola in 2001. “But I don’t think they need to be put away in solitary where they can further harm themselves.”

On Wednesday, Maine lawmakers will begin probing the legal justifications and ethical questions surrounding long-term imprisonment in solitary confines.

A bill under consideration in the Criminal Justice and Public Safety Committee would not prohibit state prison officials from isolating prisoners for even months or years at a time. But the bill, LD 1611, would restrict stays in solitary lasting longer than 45 days to prisoners who “committed or attempted to commit a sexual as-sault, an escape from confinement or an act of violence.”

Such prisoners would have the right to hearings with a special commission once they reach 45 days. The legislation would also prohibit placement of prisoners with “serious mental illness” in solitary confinement and would require regular mental health evaluations of isolated prisoners.

The bill, sponsored by Rep. James Schatz, D-Blue Hill, has garnered the support of a broad coalition of civil rights, religious and medical groups, including the Maine Council of Churches and the Maine Psychological Association.

Emily Posner with the group Mainers Against the Abuse of Solitary Confinement said she first met King while the two were working on relief efforts after Hurricane Katrina. But it wasn’t until she read more on the possible physical and mental side effects of solitary confinement that she began working with others on legislative proposals to change Maine’s law.

Supporters of the legislation recognize that isolation or segregation is an important tool for corrections officers, Posner said.

“Prisons are not nice places, and there are circumstances in which people need to be isolated from the general population,” Posner said. “We recognize that. We just think there should be due process.”

The big questions, she added, are who should be isolated, for how long and should there be additional oversight.

Maine Department of Corrections officials have said they do not put prisoners into solitary confinement. Instead, they are placed in “special management units” and segregated for either administrative or disciplinary reasons.

Maine State Prison in Warren has 100 cells where prisoners can be kept in isolation for as many as 23 hours a day. Prisoners have access to books, correspondence and religious and legal materials, however.

An average of 80 prisoners are kept each day in this special management unit, which is meant to discipline unruly prisoners or to keep guards, staff and prisoners safe.

About half the prisoners kept in segregation are there because they are being disciplined, and those prisoners stay less than a month. The other half of the unit comprises prisoners who are “administratively segregated,” and they can stay much longer, an average of four months, according to information supplied by the Depart-ment of Corrections.

Wednesday’s hearing — scheduled for 1 p.m. in room 436 of the State House — is expected to draw a sizable crowd, both for and against the bill. Schatz said he is hopeful that he can get some version to the House floor, because he believes the issue is more important than most people realize. Bill supporters point out that many of the people who spend time in solitary are ultimately released from jail.

“The sky is not falling, but I don’t think the public is being served well by this,” Schatz said of solitary confinement practices.

King, who also goes by the name Robert King Wilkerson, will not be there to testify, but he visited the State House last week to talk with lawmakers and others about his experiences in advance of the public hearing.

King had a history of trouble with the law, but in 1970 was convicted of a robbery he says he did not commit. Once in prison, he attracted the attention of jail authorities by his involvement in Black Panther efforts to improve conditions for inmates and to resist institutional racism in the prison. He was put into solitary confine-ment.

King claims he was later framed by jail authorities for an in-prison murder.

When the U.S. Circuit Court of Appeals ordered that the evidence against King be re-examined, he pleaded guilty to a lesser charge of conspiracy to commit murder. Having served enough time to satisfy the conspiracy charge, he immediately was released from prison in 2001.

King has also traveled around the world talking about his 29 years in solitary confinement and the plight of two other “Angola 3” inmates — Albert Woodfox and Herman Wallace — who have spent more than 30 years in solitary. Serious questions have been raised about Woodfox and Wallace’s convictions in the murder of a prison guard.

King said he will be watching what happens in Maine.

“I believe other states can be and will be impacted by it, whatever Maine does,” he said.

Bangor Daily News writer Abigail Curtis contributed to this report.