A North Jersey man who admitted killing his young son 17 years ago has been set free as part of a plea deal in which he agreed to tell authorities where the toddler's body was buried, even though the child's remains were not found during a lengthy search last month.

Curtis Williams said he buried the clothed body of 2-year-old Curtis McCoy under three feet of dirt on a hilly, brushy area under an elevated portion of the New Jersey Turnpike in Jersey City. The remains were not found, even though searchers sifted through soil covering hundreds of square feet of ground.

Nevertheless, the plea deal - which had reduced murder charges that carry a possible life sentence if convicted - remained in effect. On Friday, Superior Court Judge Peter Vazquez sentenced Williams to five years' probation, the maximum allowed for the charge of hindering apprehension to which Williams pleaded guilty, said Debra Simon, an assistant Hudson County prosecutor.

Authorities believe Williams was telling the truth about where he buried McCoy's body because he passed a polygraph test. Simon also noted that after so many years - the boy was killed in November 1989 - there may have been nothing left of the toddler's body.

She said the plea deal came about because the case against Williams was weak - there were only two witnesses and both may have had ulterior motives to testify against him - and prosecutors wanted to give McCoy's family closure.

"I didn't have a slam dunk of a case," Simon said. "If we go to trial for murder and we lose, and we ask him where the baby's body is, he would have laughed. And if we win, what motive would he have to tell us where the baby is?"

Williams, 40, initially was charged with the boy's murder in January 2006. At the time, he was serving a sentence for fraud for claiming McCoy as a dependent on a loan application. As part of the plea deal, that charge was also dropped.

At the time of his disappearance, the boy had been living with his mother, La Shawn McCoy, in Gifford, S.C. She allowed Williams to take the boy to his Union City home so the child could spend Thanksgiving with him.

Soon after, Williams told Newark police his son had gone missing while they were shopping. The boy's mother later moved to Jersey City and became convinced her son might still be alive and in the area.

Around the 15th anniversary of her son's disappearance, in 2004, she contacted Detective Keith Armstrong of the Jersey City Police Department major case unit. Armstrong found evidence implicating Williams, which led to the murder charge.

Williams' lawyer, Jeffrey Jablonski, said the subsequent plea deal was the only leverage prosecutors had against Williams to get him to reveal where McCoy's body was.

"If Mr. Williams knew where the body was, that was his largest bargaining chip," Jablonski said over the weekend. "I know that sounds terribly, terribly harsh, but that's the reality of the situation."