Michael R. Clark Sr. pleaded guilty late Tuesday to criminally negligent homicide in the death of his baby son in 2002.
He entered the plea during a nonjury trial on murder charges before State Supreme Court Justice Ralph A. Boniello III.
No promises on sentencing were made to Clark, 26, of St. Joseph Road, Wheatfield.
The most Clark could receive is 1 1/3 to four years in prison. Boniello set sentencing for Jan. 24.
If Clark had been convicted of murder, he could have received 25 years to life.
Second Assistant District Attorney Holly E. Sloma said the plea followed direct examination of the baby's mother.
In her opening statement Nov. 1, Sloma had said that Rachel McNally would testify that she was away on an errand Sept. 24, 2002, when Clark called her on her cellular telephone and urged her to come home because Michael Jr. was ill.
The baby was not responsive when the mother returned home, and McNally claimed that Clark tried to keep her from phoning for help.
She eventually took the baby, who was less than 5 months old, to Mount St. Mary's Hospital in Lewiston.
Doctors there concluded Michael Jr. had suffered a head injury, and he was transferred to Women and Children's Hospital in Buffalo, where he died the next day.
Dr. John Pollina, the attending neurosurgeon at Children's, concluded that the child has been subjected to trauma.
First Assistant District Attorney Timothy R. Lundquist told a County Legislature committee Wednesday that Michael Jr. had been shaken and thrown into a bassinet.
Lundquist made the comment while seeking approval for the appropriation of $25,000 to pay for the expert witnesses the district attorney's office hired to testify about shaken-baby syndrome and other technical aspects of the case.
Defense attorney Angelo Musitano had lined up experts to testify that there is no such thing as shaken-baby syndrome.
County taxpayers will have to pay for those, too, as well as Musitano's fee, because he accepted a court assignment to the case after public defenders backed out.
The high-priced experts never got on the stand in a trial that had been expected to last at least two more weeks.
District Attorney Matthew J. Murphy III praised Sloma for her work on the case, in which Murphy also took part.
"Holly did most of the heavy lifting," he said. "She was in command."
Murphy said the plea offer had been on the table for months. "I would say it was a difficult case, but I was glad to get the assurance of a conviction," he said.
"We had talked about it throughout the trial," Musitano said. "The problem was what (Clark) would admit to."
He admitted to negligence in not calling for medical help right away after he saw the baby had been injured.
"I think at a minimum the prosecution had proved he acted negligently in failing to recognize his son's condition and not calling 911," Musitano said.
He said he didn't believe McNally's story that Clark tried to talk her out of calling for help.