Mullis appeared briefly in a Philadelphia courtroom Monday to say he wouldn't challenge his return.
Mullis has been charged with capital murder in Galveston.
Police say he admitted that he placed 3-month-old Alijah Mullis on the ground and then stomped on his head until he felt the skull collapsing. The baby's body was found last week on the side of a Texas road near his child safety seat.
Authorities say Mullis stopped in Maryland, where he has family, before driving to Philadelphia and surrendering to police.
