SACRAMENTO -- A federal judge abruptly interrupted a weeks-long hearing so that he could begin considering whether the prolonged solitary confinement of mentally ill inmates in California prisons violates their civil rights.

On Thursday, U.S. District Judge Lawrence Karlton in Sacramento ordered attorneys representing inmates and the state to submit written closing arguments instead of hearing oral arguments as scheduled.

"I can't possibly absorb any more," Karlton said, expressing impatience with the volume of testimony that followed his April decision to reject Gov. Jerry Brown's attempt to end court oversight of prison mental health programs.

The solitary confinement issue is the last of four questions surrounding the treatment of mentally ill inmates that are before the judge. He already has ruled against Brown's administration on two others: He decided that mentally ill inmates on death row lack proper care and that the Department of State Hospitals also provides substandard treatment to mentally ill prisoners.

Karlton said he is still struggling to decide on the third, which focuses on use of force by prison guards. That question hinges in large part on the guards' use of heavy amounts of pepper spray on the mentally ill.

While hearing the latest dispute, the judge said earlier Thursday that he is considering ordering mental health professionals to examine each mentally ill inmate before they can be put into isolation units.

"There are people who are clearly very ill, and the likelihood of their being unable to cope with administrative segregation is very high," Karlton said.

His comments came the same day as state Senate President Pro Tem Darrell Steinberg, D-Sacramento, proposed creating a $50 million competitive grant program to help counties provide more mental health treatment as one way of reducing the criminal population. Half the money would go to aid juvenile offenders and half for adults, and it could be used in part for special mental health diversion courts.

The court hearing is the latest development in a 23-year-old lawsuit that helped lead to sweeping changes in the state prison system, including a sharp reduction in overcrowding.

Karlton and two other federal judges, with backing from the U.S. Supreme Court, have ruled that reducing the prison population is necessary to improve inmate medical and mental health treatment.

The crowding debate overlapped into Karlton's hearing on the segregation of mentally ill inmates, after the judge demanded that the administration limit the time that some troubled inmates spend in isolation. Once the administration complied, Karlton and the other judges last week gave the state until April to meet a court-ordered population cap, extending what once was a year-end deadline.

Attorneys representing inmates said the Department of Corrections and Rehabilitation sometimes keeps mentally ill inmates in segregation because they lack space in treatment facilities. To satisfy the judge, the state issued a new policy earlier this month setting a 30-day limit on housing severely mentally ill prisoners in isolation units if they have not violated prison rules. The limit is 60 days for those with mental illnesses deemed less severe.

Michael Bien, an attorney representing inmates, said keeping mentally ill inmates in isolation for any reason does more harm than good. He and fellow attorney Jane Kahn said after the hearing that most prison suicides are in administrative segregation units or on death row, and most of those are by inmates already diagnosed as mentally ill.

Patrick McKinney, a lawyer for the state, said California provides proper care and treatment within the isolation units.

The state said in court documents that inmates are transferred to other facilities if they need more intensive care. Lawyers for the state argued that there is insufficient proof to conclude that segregation causes or exacerbates mental illness and the prison system follows national psychiatric standards.