SUPER-MAXIMUM SECURITY PRISON CAN'T STOP GANG MEMBERS FROM COMMITTING CRIMES -- "60 MINUTES" SUNDAY ON CBS

Prison gangsters have managed to outwit law enforcement and turn one of the nation's toughest, most super-maximum security prisons into their criminal headquarters, Lesley Stahl reports. Her story will be broadcast on 60 MINUTES, Sunday, May 15 (7:00-8:00 PM, ET/PT) on the CBS Television Network.

The prison involved is no less than Pelican Bay State Prison in Northern California; specifically, its isolation unit called the "SHU," or Security Housing Unit, where inmates are housed in nearly solitary confinement, locked in their cells for 22 and a half hours a day, searched regularly for weapons and their personal effects x-rayed for contraband.

Yet members of the Aryan Brotherhood, Mexican Mafia, Nuestra Familia and other prison gangs are able to run thriving criminal enterprises out on the streets from inside the prison, 60 MINUTES has confirmed from state and federal investigators.

What kinds of crimes are orchestrated from the SHU? "Anywhere from murder to money laundering, bank robberies, armored-car robberies, home invasions, drug deals, prostitution," according to Epi Cortina, a former member of the Nuestra Familia who lived on the SHU for nine years.

And how easy were inmates able to get messages out on to the street? "Real easy," according to Cortina and other former gang members interviewed by Stahl.

Inmates on the SHU are able to break their isolation and scheme with one another through a myriad of clever methods, including talking through storm drains and ventilation pipes, as well as through something called "fishing," in which inmates fashion a fishing line from the threads of their underwear, bed sheets and socks and tie tiny notes onto the end. The inmates then slide the notes under the prison doors, hook their lines and reel in each other's secret messages.

Once they communicate with each other, the most effective way they get their messages to their foot soldiers on the outside is through the U.S. mail -- sending letters is one of their rights guaranteed by law. Inmates write letters using codes that have been so hard to decipher, they have been sent to the FBI's cryptologists in Washington. Inmates also embed secret codes in their intricate prison artwork that is then mailed out to their "homeboys" on the street.

"And so what happens," says Lt. Steve Perez, a senior official at Pelican Bay, "is that when this [artwork] goes out, if you're not paying attention to what's happening, if you're not looking for the indicators of how they communicate, a beautiful piece of artwork becomes a message to have someone killed." Adds Perez, "These are the most creative, the most ingenious men, deeply committed to achieving their criminal goals."

Law enforcement officials became so alarmed at the expanding influence of one of the gangs, Nuestra Familia, that it launched Operation Black Widow, the largest and most expensive investigation of a prison gang in U.S. history.

Investigators turned up 10 hit lists and prevented scores of homicides that were already in the planning stages, including a plot to murder two deputy district attorneys in California, says Steve Gruel, the lead federal prosecutor in the case. In all, Gruel says Operation Black Widow resulted in the arrest and conviction of some 150 gang members and associates.

But now what to do with them? The gang leaders were already serving life sentences at Pelican Bay. So Gruel has proposed taking the gang leaders out of the state prison and scattering them across the country in various federal penitentiaries. "If you take a [Nuestra Familia] general and put him in Marion, Illinois, or in Minnesota or some other institution in Arkansas, he's going to be a nobody," Gruel tells Stahl.

But one of Gruel's main informants in the case, Robert Gratton, a former high-ranking member of Nuestra Familia, disagrees. He says the plan will spread the influence of the gang to other parts of the country.

"Not only are they going to run [their criminal organization from the new prisons]," Gratton tells Stahl, "they're going to be able to recruit and they're going to prosper." In fact, Gratton adds, "it's [already] too late. They've re-established new lines of communication, new contacts."

Pelican Bay's Lt. Steve Perez agrees, saying, "These men will go out into the federal system and continue to branch out, to create new gangs and continue their gang activity."