Henry Hill, the gangster who was the inspiration for the 1990 film "Goodfellas," opted out of the witness protection program, as did mob turncoat Sammy "the Bull" Gravano.
But those witnesses' decisions to leave the program make them the exception to the rule, Shur said.li
After a witness agrees to testify for the prosecution, he or she may be eligible to start receiving protection. Shur described an effective way of choosing where to relocate a witness.
"I would say to them, 'Tell me what's your favorite place in the U.S.?' " Shur said, "and they'd say, 'I always wanted to go to Hawaii,' or that they had family in Texas or Florida. And in my mind that's three places that they are not going. Because when you tell me you want to go to Hawaii, I know you have told all your friends that."
Deputy marshals take the witness and the witness' family and move them to another area, Shur said. Sometimes, they start in a hotel. Sometimes, they are near other witnesses -- although they'd never know it, he added.
"In the beginning when the witnesses were moved off to another city, we'd run into the problems you would expect -- what to do about a driver's license, Social Security cards, how do you get him a job, money, what happens if you need Medicare care, what about the house he owns, the furniture, and so on."
Witnesses get help finding a job, but they aren't always compensated.
"The program has nothing to do with reward money, nothing. They get money for a period of time, and then it stops," Shur said. "We used a formula. If you are a family of four in New York, you would get more money than a family of four from Corpus Christi. It's based on cost of living, and it wasn't based on the value of the testimony."
Shur said his work protecting witnesses put his family's life in danger. "There was a threat against my wife. I was told that there was an individual who had my name and my wife's name in his address book and that he had a contract from the Medellin Cartel to kidnap my wife and learn where a particular witness was living. And I immediately asked for protection for my wife."
Today's witness protection program faces the added burdens of the digital age. Facebook, Google, texting and the instant access to information via the Internet and smartphones provide new challenges to keep the identities of witnesses a secret.
"The modern world of technology, because there is more information out there, it's that much more important for our people to be vigilant and for us to be vigilant," said Harlow of the U.S. Marshals Service.
Vigilance plays a role, but Shur suggested another factor may also play an important role.
"Luck, you have to throw in some luck," he said. "You can't go this many years with this many witnesses without some luck in this thing."