Are California prison officials keeping dangerous inmates away from each other or inflicting unnecessarily cruel punishment? The issue of indefinite solitary confinement, a common practice at state institutions, is worth a closer look. The matter inspired 30,000 prisoners in 11 state facilities to launch a massive hunger strike this week, the largest of its kind in California history.

Prison officials say some inmates must be kept away from the general population for the safety of all, and they're correct without question. But the practice is overused: Inmates held in the so-called Security Housing Units are typically locked up in excruciatingly small cells for 22-1/2 hours a day -- sometimes for decades. Amnesty International has called this extended confinement "degrading treatment" that violates international law.

There's no chance of "correction" with this group, many of whom have been accused of gang activity without ever having been convicted of gang-related offenses. Prolonged isolation like this subjects prisoners to mental illness, even psychosis, and the rate of suicide is 42 percent, based on 2006-2010 statistics -- even though inmates in solitary comprise just 2 percent of the prison population.

Perhaps the solution is to place a maximum length on the amount of time that inmates can be placed in isolation and, even then, only for clear, established reasons. Perhaps the question of their continued isolation deserves a new hearing more often than the current four-year interval. In any case, the practice deserves a fair, detailed hearing.