As part of the "I Challenge" series looking at individuals who have challenged authority around the world, Rene Enriquez - a former leading member of the Mexican Mafia, a notorious US prison gang - tells the BBC about his experiences as a mafioso and his decision to quit the organisation.
In an old arrest photograph, Rene Enriquez stands defiantly, his criminal history boldly stamped across his torso.
Rene rose to the highest ranks of the Mexican Mafia
One tattoo on his chest shouts for attention. It's a black hand, symbol of one of America's most violent gangs, the Mexican Mafia.
Rene, 43, formerly known as Boxer and once ranked as a Mexican Mafia "Godfather", is serving several life sentences for killings committed in the name of the gang.
For nearly 20 years, nothing stopped Rene in his climb from street thug to top leader in the Mexican Mafia.
He killed men and ordered hits, ran elaborate drug rings, laundered money, and mobilised thousands of Latino street gang members for battle.
Remarkably, Rene committed many of these crimes while serving a life sentence in one of America's most fearsome "Supermax" prisons using complex systems of communication and subterfuge.
But after years of this way of life, he began to question what he was doing.
"I was a leading member of the Mexican Mafia until one day, I decided that I'd had enough," he explains. "I decided to defect."
The Mexican Mafia is one of the "big five" prison gangs that turned California's criminal justice system on its head, operating with near-impunity behind bars.
California runs America's largest prison system, with more than 160,000 inmates. For years gangs controlled drug sales, extortion and other criminal networks in prisons.
"You were immediately elevated in your position in your neighbourhood once you got out of prison," says Rene, who joined the gang in his late teens.
"The girls loved you, the guys respected you and you learned a lot in the joint. It's crazy, but that's the way it is."
He says he became addicted to the violence.
"The more notches you have on your belt, the more ferocity people see you as possessing, and the greater you become."
As tough sentencing laws packed the prisons, the gangs grew larger. So they looked to the streets to increase power and profits.
California responded by confining gang leaders like Rene in harsh isolation. For 13 years he was locked down, alone, in a windowless cell with only an hour of solitary exercise in a concrete pen.
But instead of being "broken", Rene deepened his commitment to the gang. He learned complex secret codes to communicate with other members and on the streets.
He adopted the gang's punishing exercise routine and plunged into study, reading hundreds of books on philosophy, leadership, modern corporations and military history.
He learned how to harness the power of fear under the most extreme conditions. But life in solitary took its toll. The gang descended into internal strife.
Exhausted, Rene says the final straw came when some members proposed widening the war against rivals by targeting their families.
"That's when I knew it was time to leave," he says. But killing "Boxer" off was the hardest part. That's all I ever knew. That's who I was".
"I was ashamed of leaving the organisation, something that I've killed for, dedicated my life to. Twenty years of my adult life, and I'm walking away from it."
In gang culture, defection is the ultimate disloyalty and anyone who leaves risks being killed by other members of the gang.
To get out of the Supermax, Rene was forced to betray his comrades and reveal the gang's innermost secrets to authorities in a thorough de-briefing process.
Rene's information proved vital in prosecutions of top Mexican Mafia members, in understanding how the gang infiltrated other organisations, and manipulated the prison system's rules.
But it also put him on the gang's hit list.
"He has become their number one priority," says gang investigator Robert Marquez, of the California Department of Corrections. "If ever they get a chance, they want him dead for what he's done."
He now lives in Lancaster State Prison, a special unit north of Los Angeles in the Mojave Desert designed to protect gang defectors from retaliation.
He runs a prisoner outreach group to educate children about the realities of gang membership and helps the authorities increase their knowledge of the Mexican Mafia.
Rene's hopes are focused on making parole. But redemption is a daunting task, given his bloody history.
"The reality is that I believe that I will die here," he says. "I believe that I will never get out."
On Thursday you can read about a Kenyan-born British Muslim who is training to become a female Imam.
You can listen to programme on the BBC World Service at 0806 GMT on Thursday.