The father of “Peter Boy” Kema passed a polygraph test Wednesday as to the whereabouts of the body of the 6-year-old son he abused for years.

The lie detector test was mandated under a plea deal that shaves five years off his sentence.

Peter Kema Sr. evidently told Hawaii County police the truth in April when he revealed that in 1997, after unsuccessfully trying to burn his dead son’s body, he placed it in a box and dumped it into the ocean at a site in Puna.

Kema Sr. and his wife, Jaylin, were indicted after nearly 20 years on second-­degree murder charges in April 2016 for Peter Boy’s death. Kema Sr. claimed he had given the boy to a woman in Honolulu and that he had not seen the child since.

But prosecutors cut a plea deal with Kema that required him to lead police to his son’s remains to get a concurrent sentence for manslaughter, which carries a maximum of 20 years, and hindering the prosecution of his wife, a five-year term.

If that failed to turn up any results, he was required to pass a lie detector test on what he did with the boy’s body. Had he failed the test, he would be facing a 25-year combined sentence for the two crimes, to which he pleaded guilty April 5, Hawaii County Deputy Prosecutor Rick Damerville said.

Kema will be sentenced at 8 a.m. July 24 before Judge Glen Nakamura in Hilo Circuit Court.

Kema’s manslaughter plea included admitting that he caused his son’s death by failing to get medical help and recklessly causing his death by multiple assaults.

On April 23 Kema led police to the location in Puna where he claimed to have dumped his son’s body into the ocean.

The Coast Guard, Department of Land and Natural Resources and police personnel, after a weeks-long search, were unable to find any remains, police said.

Damerville said that with the passage of time and having put the body into water, it was unlikely any remains would be found.

“We knew it was going to be difficult, but we had an obligation to the family to try,” Damerville said.

Prosecutors said Peter Boy likely died of septic shock from a large, festering wound on his arm, and that both parents failed to seek medical attention.

“If we got a fair and unbiased jury that can put aside that he concealed this homicide for a long time, it’s very likely they would have returned a manslaughter verdict,” he said.

Child Welfare Services documents show Kema began abusing Peter Boy from the time he was an infant, who was born with respiratory problems. Peter Boy suffered broken bones, was chained and was even forced to eat dog feces.

Kema also abused the Kemas’ three other children, but Peter Boy got the worst of it, his siblings said.

Jaylin Kema pleaded guilty in December to manslaughter in exchange for her testimony against her husband, if his case had gone to trial. She was sentenced to one year in prison in June but was freed on supervised release in April after serving a year.