Roberto Valencia, 28, of Modesto turned himself in to the Modesto Police Department about 6 p.m. Saturday.
He is a suspect in a case involving an injured 19-month-old Modesto boy who was found unresponsive by Valencia's mother at 2 p.m. Thursday afternoon, when she returned to a home in the 400 block of Sixth Street. Valencia, who had been home with the boy, has been arrested on suspicion of child abuse, torture and mayhem.
The child is in critical condition at Children's Hospital & Research Center Oakland, a nursing supervisor said.
Sgt. Craig Gundlach, Modesto police spokesman, said Valencia told detectives that he turned himself in as a result of publicity about the case.