DENVER (AP) — An appeals court on Thursday denied a request by a federal prisoner convicted of killing three people behind bars to be released from solitary confinement, where he has been held the past 30 years.

A three-judge panel of the 10th U.S. Circuit Court of Appeals on Thursday denied the request from inmate Thomas Silverstein, 62, to leave solitary confinement at the federal Supermax prison in Colorado.

The ruling identifies Silverstein as a top leader of the Aryan Brotherhood prison gang. Since entering the federal prison system in 1978 on a bank robbery conviction, he’s been convicted of killing two other inmates and a correctional officer.

“Not only has Mr. Silverstein established his credentials and legendary status with various gangs by committing multiple murders, but retirement from the Aryan Brotherhood does not exist,” the court ruling states.

The ruling states releasing Silverstein from solitary would create a substantial risk to himself, officers and other inmates. It states that the U.S. Supreme Court has identified Silverstein in its rulings as the sort of prisoner who has nothing to lose by committing further crimes in prison because they’re never getting out of the system.

Silverstein, represented by law professors and students at the University of Denver, had argued that his extensive time in solitary violated his constitutional rights. Attempts to reach one of his lawyers were not immediately successful on Thursday.

Silverstein was convicted of killing two other inmates in the federal prison system and a correctional officer at the federal penitentiary in Marion, Illinois.

From Illinois, Silverstein went to the U.S. Penitentiary in Atlanta, where he was kept in a specially constructed isolation unit as one of the most heavily guarded prisoners in the federal system.

Silverstein was freed from his cell in Atlanta when Cuban inmates there staged a riot in 1987. However, the rioters later bound Silverstein in handcuffs and shackles and turned him over to federal authorities after deciding among themselves that he shouldn’t be allowed to roam free in the burned-out prison. A Justice Department spokesman at the time said he believed the rioting Cubans saw Silverstein as a threat.

The appeals court on Thursday noted Silverstein waited until 2007 to bring his claim and said he was barred from complaining about the conditions of his confinement before 2001.

In its ruling, the appeals panel stated, “thirty years is indeed an extraordinary length of time to live in segregation, under any conditions.” But it also noted that, prior to 1988, Silverstein committed at least three brutal murders, was implicated in two others, assaulted three staff members, tried to escape by posing as a United States Marshal and possessed weapons and handcuff keys.

“My Silverstein’s history with regard to both his violent conduct and leadership in the Aryan Brotherhood makes this a deeply atypical case and it is clear his segregated confinement is commensurate with ongoing prison security concerns,” the ruling states.

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