MEMPHIS, Tenn. (AP) — Prosecutors say a Tennessee man has pleaded guilty in his 6-month-old daughter's death, which was initially believed to have been caused by a traffic accident.

The Shelby County district attorney's office said Monday that 29-year-old Atu Campbell has been sentenced to 20 years in prison. He pleaded guilty to second-degree murder and aggravated abuse of a child under 8 in a court-approved settlement.

Police said Campbell was driving a car that left the road and struck a fence in October 2012 in Memphis. His daughter, Anyiah Nicole Nabors, was found face down on the rear passenger floorboard. A baby seat was upside down and improperly secured.

But an investigation showed the baby had fractured ribs and a lacerated liver — injuries that were inconsistent with the traffic accident.