Sacramento lawmakers are holding a hearing today to examine the state's controversial use of isolation units at Pelican Bay State Prison and three other correctional facilities.

The hearing was called following a three-week hunger strike last month by inmates who complained they were being unfairly held for years in extreme isolation.

Officials say that housing prisoners in these isolation units is necessary for those with dangerous gang affiliations. But how prison officials determine an inmate's connection to a gang can vary from one prisoner to the next.

Arturo Castellanos is one inmate jailed in the isolation units. In 1979, he was convicted of murder in LA County and sentenced to 26 years to life. After a series of assaults behind bars, the state determined Castellanos was a member of the Mexican Mafia prison gang and sent him to Pelican Bay, on California?s remote north coast.

The stark, windowless cells at the prison's Security Housing Unit -- known as SHU -- were designed to incapacitate inmates like Castellanos. But authorities say he continued to command gang members on the street through edicts smuggled out of prison on tiny scraps of paper.

Peter Hernandez, an assistant US Attorney for California's central district, said, "I was just amazed that an individual who no one has seen for generations was able to control the violence and illegal criminal activity of an area that he hasn't been to in more than three decades."

Hernandez said in 2004, under Castellanos's guidance, a Latino street gang known as the F13 launched a turf battle against African American rivals, triggering racial violence in the Florence-Firestone area north of Watts. More than 20 people were killed, and in 2007 the feds indicted 104 suspects.

But prosecutors chose not to pursue Castellanos. To do so, the government would have had to pull him out of Pelican Bay for court hearings. Hernandez said it was safer to keep him in isolation.

"It's important that that person -- Castellanos -- not to be let out, because he holds sway over gang members to do things they would otherwise not want to do."

During a tour of Pelican Bay's security housing unit last week, officials underscored that the bleak conditions are necessary to deal with dangerous gang members like Castellanos. Here inmates spend 23 hours a day locked in windowless cells, with one hour of exercise in an adjoining concrete pen. Acting warden Greg Lewis alleged all four leaders of the recent hunger strike, including Castellanos, were in the upper echelons of different gangs

"Each one of them are very intelligent, very manipulative and possess the intellect to orchestrate what they did," Lewis said.

Gang Ties Vary From One Inmate to Another

However, not all the inmates housed in the SHU are alleged gang leaders. For example, Ernesto Lira was a petty thief serving time for minor drug possession. He was sent to Pelican Bay for an indefinite term, after authorities determined he was associated with a violent Latino prison gang.

But Lira was not accused of actually doing anything tangible for the group. The key piece of evidence against him: a drawing found in his locker that allegedly contained gang symbols.

"My first two months it was hard to get used to the fact that I'm going to be here," Lira said. "I looked and thought?maybe in a month or two they'll realize that this is all a mistake and kick me out of here."

There was a way out of isolation, officials told Lira. He could debrief, or snitch, on other gang members. But as a judge later determined, Lira couldn't do that because he wasn't a member of any gang. He wasn't released from the SHU until his release from prison eight years later.

Lira eventually won a judgment in US District Court against the Department of Corrections, in part for psychological damage he suffered while locked in isolation. Prisoner right's attorney Charles Carbone has represented dozens of inmates locked in Pelican Bay's SHU.

"In Ernesto's case, I think it's very emblematic of the fact that people can be placed in solitary confinement for the littlest of reasons: for having a drawing, for having an address in an address book, without confirming or denying whether that address was used for furthering gang activity," Carbone said.

Changes for Isolation Units on the Horizon

Corrections officials are now considering changes that could help keep inmates like Lira out of isolation units. For instance, an inmate would have to commit a specific offense for a gang or be involved in an active conspiracy. Also under consideration are incentives to encourage inmates to work their way out of the SHU through better behavior. This is known as a step-down program and usually doesn?t require inmates to debrief or snitch.

Rene Enriquez likes this idea; he is a former Mexican Mafia leader who spent ten years in the SHU and then dropped out.

"That's a wonderful concept," Enriquez said. "I've never heard of that before. It would have saved me a whole lot of grief. It might have taken me off the hit list."

His debriefing video has attracted more than 500,000 hits on YouTube. Since then, Enriquez has cooperated from behind bars in several high-level gang prosecutions. He said the department is right to stay tough on gang leaders, but it should take a more nuanced approach towards others, including offering a less traumatic path out of the SHU that doesn't include debriefing, or snitching.

"I met with [Mexican Mafia] members -- active -- and they told me I want to drop out but I don't think I can do it," Enriquez said.

"Fifty percent of the members of the Mexican Mafia would gravitate towards dropping out if it was less traumatic." At today's hearing, corrections officials are expected to discuss a range of reforms that could include modifying the debriefing policy.

But officials emphasize two things: any big changes could take months, if not years to hammer out, and the department will continue to use Security Housing Units for inmates who pose a major security threat.

This report was produced in collaboration with California Watch, a project of the Center for Investigative Reporting.