Prison con games are as old as lockups themselves.
But there are few as potentially dangerous as the hustle that seems to have snared a worker at Clinton Correctional Facility in upstate New York — and allowed two convicted murderers to escape.
The civilian worker, Joyce Mitchell, was assigned to the maximum security prison's tailor shop, where authorities said she had "befriended" the inmates, Richard Matt and David Sweat. Over the course of a couple months, Matt charmed her, apparently leading her to believe they were in love, sources familiar with the case told NBC News.
Inmates even have a name for the way they meticulously groom and slyly manipulate prison workers. It's called "downing the duck."
Workers are trained to protect themselves against the technique, but it requires the discipline to keep inmates at an emotional distance — a difficult task when your job requires you to be around them all day, experts and corrections workers say.
Revealing personal details are often used as a way to begin the process of sharing sympathies — and favors.
"An inmate doesn't want a staff member to see him as a criminal," said Gary Cornelius, a retired lieutenant for the Fairfax County Adult Detention Center in Virginia and the author of "The Art of the Con: Avoiding Offender Manipulation."
"The inmate would rather the worker see him as just a person with problems, a person who needs help, a person who's not that bad."
"When that happens, they've crossed the line."
The grooming process can take months, or years, relying on elaborate techniques that are passed from inmate to inmate across generations. Corrections officers have also collected them, and included them as lessons in training seminars and online forums.
"They try to make you forget who they are as an inmate and try to connect with you on a personal level, so you forget your prescribed role and can't be objective. You see them as a brother, a son, whatever. It blinds you," said Anthony Gangi, who trains corrections officers to protect against inmate manipulation and hosts an internet radio show called "Tier Talk."
The connections can range from rooting for the same sports team to commiserating about romantic troubles.
"Inmates have time to study everybody, and figure out what tactic will work best with a certain individual," Gangi said. "They find a game that fits specifically for that person."
Typically, the scam is used to obtain favors or contraband. But they are also used for more nefarious means.
One of the most egregious schemes occurred in a Baltimore prison, where a gang member essentially ran the institution and impregnated several corrections officers, a scandal exposed in 2013 by a federal racketeering indictment.
Two decades ago, the wife of an Oklahoma prison warden helped a convicted killer escape after she fell in love with him while working in in a prison pottery program.
Vito Dagnello, who worked three decades as a corrections officer for the Suffolk County Sheriffs Office in New York, said corrections officers are typically better equipped than civilian prison workers to guard against inmate manipulation. The officers generally get more rigorous training, and are paid better, he said.
But in a situation where a civilian worker like Mitchell might spend her day working alongside inmates, there should be corrections officers present at all times to protect that worker, Dagnello said. "She probably saw these two individuals every day for months, maybe longer."
Dagnello, president of the American Correctional Officer, an advocacy and fraternal organization, said there are some basic guidelines to protecting against con jobs: Be firm, fair and consistent in watching over inmates; never reveal any personal information; and don't think about them outside of work.
"You have to watch your back all day long," Dagnello said. "That's what makes it such a stressful job."