The Lake County State's Attorney's Office says the child, 4-year-old Skylar Mendez, spilled juice on an Xbox while at home with 19-year-old Johnathan Fair.
According to an indictment, Fair punished the child by beating her and allegedly kicked her down the hallway of the home.
After the girl passed out, Fair brought her to the hospital and gave doctors conflicting accounts of what happened, authorities said.
Fair said he was babysitting Skylar when the young girl fell and hit her head. He later allegedly admitted to police to shaking and beating the 4-year-old.
Doctors said Mendez had brain swelling, and it did not appear to be the first time she had it. Hospital staff noted previous signs of abuse and shaking dating back several months.
Fair was indicted on four counts of first-degree murder. He's being held at the Lake County jail, where his bond was set to $5 million.
Fair is scheduled to appear before a judge on Feb. 17.
If convicted, Fair may face life in prison as prosecutors are reportedly seeking a natural life sentence.