Stolen innocence: The battle against modern-day slavery in the U.S.

ATLANTA — Maybe it was the defiant glint in her eye. Maybe it was the way she dragged her feet on the way to join the other underage girls in tube tops and 8-inch heels hawking their bodies in a bad part of Atlanta. Keisha Head wasn't sure. But somehow Sir Charles always knew when she was considering trying to escape.

"You better not be thinkin' 'bout leaving," the pimp would say. "You know what's gonna happen."

Sometimes, if he sensed Keisha needed reminding, the big man would shove the then-16-year-old into his Mercedes-Benz and drive her to the cemetery. There he'd strip off her clothes and leave her curled up next to a headstone, sobbing, to contemplate how nobody would notice if she — a runaway and a prostitute — went missing.

"I know grave diggers," he'd say when he came to collect her 30 minutes, 45 minutes, an hour later. "We could just throw you in a hole when they're burying someone else."

At the time, Keisha, now 31, was considered a delinquent. Now lawmakers are beginning to recognize she was a slave.

With job descriptions ranging in scope from prostitute to waiter to maid, more than 150,000 people in the United States are living in slavery, according to the U.S. Department of Justice. Their stories are as different as their backgrounds. There's the boys choir from Zambia that was forced to sing seven concerts a day then locked in a trailer in Texas while their benefactors collected the cash. There's the case of 400 Thai agricultural workers who came to Seattle looking for salaried work picking apples and wound up shut in wooden shacks with no pay. Researchers estimate close to half of today's victims of human trafficking are people like Keisha who have been coerced into the sex industry.

Sex slaves are the most profitable slave in the modern world, according to Siddharth Kara, a fellow on human trafficking at Harvard University and author of "Sex Trafficking: Inside the Business of Modern Slavery." On average, a sex slave costs $5,000 in the United States and, before escaping or dying, generates profits exceeding $135,000. There is little risk for exploiters because, more often than not, it's girls like Keisha — and not the pimps who manipulate them — who wind up behind bars.

There are some state and federal laws in place to fight the practice, but prosecutions and convictions are rare.