The U.S. Bureau of Prisons has agreed to pay a $175,000 settlement to the family of a convicted killer who committed suicide at Supermax at Florence after the prison system failed for decades to treat his mental illness.

Robert Knott’s aunt filed a civil lawsuit against the U.S. in federal court in Denver after he killed himself at the U.S. Penitentiary Administrative Maximum in Florence, or Supermax, in September of 2013.

The highest security prison in the U.S. left Knott to “languish in solitary confinement” for more than a decade without adequate mental health treatment, the lawsuit said. Correctional officers then ignored signs that Knott’s psychological condition was deteriorating in the weeks and days leading to his suicide, the lawsuit says.

The lawsuit, filed by Denver attorneys Kathryn Stimson, Eric Olson, Abigail Hinchcliff and Jason Murray, was settled in February. In paying the settlement, the U.S. did not admit guilt, according to the decree.

“This is just another tragic example of our government’s mistreatment of the mentally ill,” Stimson said. “The prison put this seriously mentally ill man in solitary confinement, against their own policies, ignored the fact he was psychologically deteriorating and waited until he killed himself.”

Solitary confinement amounts to torture for anyone, Stimson said.

“Our government has no business putting anyone there, let alone people like Mr. Knott with serious mental illness,” she said.

Knott suffered symptoms of mental illness most of his life. His mother fatally shot his father when he was 15. He was sentenced to federal prison in 1988 on a kidnapping charge. He was diagnosed with schizophrenia in 1989.

On several occasions, Knott unsuccessfully attempted suicide including an attempted hanging in 1992 in an effort to protect himself from white bugs.

Before Knott committed suicide, six other Supermax inmates had committed suicide and many others had mutilated themselves in suicide attempts that included swallowing razor blades and cutting themselves with glass, according to the lawsuit.

In the months leading up to his suicide, Knott refused to wear clothes and was found “babbling incoherently at his door, changing voices and tones randomly.” He also was seen drinking the dirty, soapy water out of the bottom of his shower.

After he was told he would be placed in a psychiatric prison facility in Atlanta where he would be housed with other prisoners after decades of solitary confinement he began experiencing severe anxiety, the lawsuit says.

He began regularly yelling, screaming, and talking incoherently to himself. He screamed that he was “John Greschner,” an inmate who was notorious among Supermax prisoners for tunneling his way from his cell to the prison yard. For four days leading to his suicide he refused food trays, the lawsuit says. The day before his suicide he threatened to swallow razor blades.

“But despite the evident signs of mental deterioration and suicidal impulses, the guards on duty did not place Mr. Knott on suicide watch or remove him from his cell for observation or mental health treatment,” the lawsuit says.

Against prison rules, he covered his cell window.

Knott committed suicide at 7 p.m. on Sept. 7, 2013 by hanging himself by his bedsheet, the lawsuit says.

Kirk Mitchell: 303-954-1206, kmitchell@denverpost.com or @kirkmitchell or denverpost.com/coldcases