A 26-year-old Rochester man changed his plea to guilty after he caused severe head trauma including skull fractures to a then 4-month-old last year.

James John Mentz, 23, is undergoing a pre-sentence investigation on one count of malicious punishment of a child causing great bodily harm.

According to police reports, Mentz and his girlfriend took the 4-month-old to Mayo Clinic Health System in Austin at about 7 p.m. July 28, 2011, as the infant suffered a head injury. Police were dispatched after hospital officials grew concerned over the injury, as Mentz claimed the baby fell out of a chair. The baby was airlifted to St. Marys Hospital that night.

Mentz later told police he had put the infant in a large chair with pillows in the living room about two feet off the ground and stepped into the kitchen to get a bottle of milk. Mentz said he heard a thud and a rattle, then walked into the room to discover the baby on the ground crying, according to the police report. He said he then texted his girlfriend, and said the injuries weren’t serious but he would wait until she got home to decide whether to take the baby to the hospital, as Mentz didn’t have a license.

The girlfriend’s brother then came by, and offered to take Mentz and the infant to the hospital, but Mentz refused and said he’d rather wait for his girlfriend. The brother told police the infant’s eyes were closed and he wasn’t really moving.

When the girlfriend got home, she saw swelling on the back of the infant’s head. She told police she had asked why Mentz hadn’t taken the infant to the hospital.

Hospital officials told police the large bumps on the back of the baby’s head weren’t consistent with a two-foot fall, even if the baby had hit his head on a nearby swing chair, according to police. The baby was diagnosed with several skull fractures, acute and chronic subdural hematomas, and retinal bleeding, among other things. There was evidence of new and old bleeding into the baby’s brain as well, according to the police report. At the time of the report, the infant had increased instances of seizures and was sedated on a ventilator for a time.

The Mower County Attorney’s office could not release an update on the child’s condition.

The girlfriend had told police the baby had been ill for a month before the injuries, acting spaced out at times before coming back to his normal self, according to the police report. The infant also got sick and projectile vomited for several days, which caused Mentz and the girlfriend to have the infant hospitalized for two days. The infant had a gastrointestinal check-up the morning of July 28, 2011, because of a previous medical condition, and doctors had found no signs of mistreatment then.

Mentz first appeared in court in August of last year, eventually posting bail and was released on conditions awaiting trial. He violated his conditional release in April after testing positive for cocaine use.