A Standish man has pleaded guilty to manslaughter in the 2015 death of his 3-month-old son.

Eugene “Charlie” Martineau had pleaded not guilty to a murder charge in the death of his son, Leo Josephs. Martineau on Wednesday pleaded guilty to the lesser charge after prosecutors agreed to drop the murder charge against him, the Portland Press Herald reported.

Martineau will spend between 10 and 15 years in prison. The lawyers could not agree on the length of the sentence so a judge will decide.

Martineau’s lawyers agreed not to ask for less than a 10-year prison sentence, and prosecutors said they would not seek more than a 15-year sentence and 12 years of probation after his release.

Leo Josephs died in October 2015, three days after he was taken to Maine Medical Center in Portland. An ER doctor said the infant had “a constellation of new and old injuries,” including massive retinal hemorrhaging, 24 rib fractures, a broken ankle and a bad chest bruise, according to prosecutors.