A Missoula man has pleaded guilty to smothering a 5-month-old infant last spring.

Marc Allen Palmer, 26, will be sentenced July 18 by special District Court Judge James Wheelis.

Originally charged with deliberate homicide, Palmer pleaded guilty to an amended charge of negligent homicide on Monday as part of a plea agreement.

Palmer also pleaded guilty to felony criminal endangerment for covering the mouth of the infant’s sibling, and entered an Alford plea to a felony for evidence tampering, meaning he admits that the prosecution could prove the charge at trial.

Chief Deputy County Attorney Jason Marks said he will be recommending 40 years in prison, the maximum possible sentence for Palmer. Palmer has been in custody since he was arrested in July.

According to court documents, emergency responders were called to a Missoula home on March 30, 2016, after a report that infant Brayden Beal wasn’t breathing. The infant was taken to the hospital, where he was pronounced dead.

Medical staff noticed bruising around the baby’s mouth, according to a court affidavit.

Investigators later learned Palmer — who is not the baby's father — and the child’s mother had been staying with Palmer’s mother. She told detectives she had woken up the morning of the baby's death and heard Palmer saying “knock it off, Brayden.”

An autopsy of the infant determined that he died of asphyxia by smothering, and found bruising around the child’s nose and mouth, and a tear on the skin inside of his lip.

While Palmer told police that blood on baby wipes found in the home was his because he used them to clean up after waking up with a bloody nose, DNA tests later matched the blood to the baby.

Palmer has a juvenile criminal record in Washington state, where according to court records he was charged with sexually assaulting an 8-year-old girl on six occasions over the course of a year when he was 15. He would later plead guilty to charges of child rape and child molestation and was sentenced to two years of community supervision.