Edward Tuinman changed his plea to guilty Wednesday to a charge of felony child abandonment in the desertion of his badly abused, retarded and mute 7-year-old son, Eddy, at a freeway rest stop near Boise.

Tuinman, 29, formerly of Sandy, Utah, entered the plea before 4th District Judge Alan Schwartzman, who set sentencing for May 10.In exchange for the plea, prosecutors agreed to seek a fixed 7-year prison term or an indeterminate 14-year prison term. Either way, Tuinman would spend a maximum of 7 years behind bars under the recommendation.

The charge carried a maximum 14-year prison term.

The developmentally retarded boy was found half-naked, soaked in urine and shivering in a corner of a bathroom at the rest area Jan. 4. Truckers who found him notified authorities.

An examination by a physician indicated the boy had been severely abused for years and had suffered injuries that included several broken bones and cigarette burns.

Ada County Sheriff Vaughn Killeen called it the worst case of child abuse he had ever seen.

Tuinman told Schwartzman Wednesday he had only a 7th-grade education and that he'd been been having a lot of problems with Eddy when he abandoned him.

"I couldn't put up with him no more," Tuinman told the judge. Tuinman said he tried to get help for the boy but was unable to. Ada County Deputy Prosecutor Jay Rosenthal called that claim "pure nonsense."

Rosenthal said it was Tuinman who removed Eddy from a facility in Salt Lake City despite the urgings of staff who begged him to leave the boy there.

Meanwhile, Tuinman still faces child-abuse charges in Yakima County, Wash., where he faces a maximum of 25 years behind bars if convicted.

Rosenthal said he is reviewing felony child abandonment charges against Tuinman's wife Debra, 28, and said the charge against her may be dropped.

Eddy remains in the custody of the Idaho Health and Welfare Department and officials said only that he is continuing to receive special attention and is making steady progress.

The Tuinmans were extradited to Boise Jan. 17 from Salt Lake County, Utah, where a theft complaint against them was dismissed.