At issue are cases stretching back more than two decades that claim overcrowding is the cause of poor medical and mental health treatment. Courts already have found the care so poor that it violates inmates' constitutional rights.
Inmates' attorneys argued Tuesday that releasing tens of thousands of prisoners is the answer.
If the panel agrees, it could order the population cut by one-third in California's 33 adult prisons. That would lead to the early release of some 52,000 inmates.
Closing arguments are expected to last through Wednesday. Afterward, the judicial panel must decide whether overcrowding is indeed the cause of the poor medical and mental health care.
If that is the finding, the judges then must determine whether to release inmates early and how such a release order would be implemented. Public safety also will factor into their decision.
