Three weeks ago, while preparing to go to jail, Paris Hilton sauntered out her front door with a Bible tucked under her arm—facing outward so the cover would be clearly visible. So it wasn’t a shock that it took just three days in prison before Hilton found God. She told Barbara Walters that she had “become more spiritual” and that God had given her a second chance.

There’s a long tradition of jailhouse conversions; many are temporary, aimed at gaining leniency from judges, while others seem genuine. Malcolm X discovered Islam while in a Massachusetts state prison. Oklahoma-bombing conspirator Terry Nichols claimed to have worn out four Bibles during his trial, and serial killer David Berkowitz—Son of Sam—converted from Judaism after an inmate told him Jesus Christ loved him and wanted to forgive him. Chuck Colson, special counsel to President Richard Nixon, once described as the “evil genius of an evil administration,” was facing arrest over Watergate charges when he read C. S. Lewis’s “Mere Christianity.” He converted before he went to prison, then went on to create Prison Fellowship, a volunteer ministry in more than 1,600 U.S. prisons that aims to help inmates “transform their lives through Christ.”

What is it about being behind bars? “I discovered that prison is an incubator for new believers because everything else is stripped away, so you think about what really matters in life,” Colson told NEWSWEEK last week. As Samuel Johnson said, The hangman’s noose marvelously concentrates the mind. John A. Thompson Jr., executive director of Kairos Prison Ministry International, an outreach program in 300 prisons, believes it’s the isolation: “You have to be in a prison around inmates to understand how disillusioned and rudderless they feel.” What changes them, he says, is when they “begin to understand that there are people out there who care about them. Maybe there’s a God who actually cares about them.”

How can we tell if Hilton’s conversion is real? With 30 years of working with prisoners, Mark Earley, president of Prison Fellowship, has identified three things that indicate a genuine change of heart: “humility, accountability and involvement in local faith communities over time.” Could humble churchgoing be hot? Colson—who faced much skepticism about his own conversion—hopes so: “If she’s serious about it, she could do a lot of good with her life.”