JACKSONVILLE, Fla. -

A 16-year-old charged with murder, aggravated child abuse and sexual assault in the death of a 1-year-old girl pleaded not guilty in court Wednesday.

Javarris Lane is accused of killing Alexandria Williams.

Williams had been hospitalized in critical condition and died days later. Lane's charges were eventually upgraded to murder.

Jacksonville police were called to a home in the 2200 block of West First Street in Northwest Jacksonville on Sept. 25.

Police said they went into the back bedroom and found an adult trying to perform CPR on the unresponsive infant on a bed.

Lane, with his father present in the home, told officers the child fell from a bed in the room where she was playing a game, according to police.

Police said there was a twin bed in that bedroom that measured 20 inches from its highest point to the floor.

Lane initially said the girl had just been sitting on his lap while he was playing a video game, and he then placed her on the twin bed, police said. Lane told police that the girl then must have rolled off the bed on her own, police said.

Investigators said they explained to Lane that the distance from the top of the bed to the floor was "not reasonable for the fall to be the cause" for the child's severe injuries, according to a police report.

Police said Lane then admitted that the girl began crying, so he picked her up and shook her, and while he was shaking her, the girl's head hit the dresser twice. Police said Lane used a doll to show how he shook the child and struck her head on the dresser.

Lane was arrested and booked into the Duval County Jail. His next pretrial hearing is set for Nov. 16.

The Department of Children and Families is also investigating.