Newark officer Louis Santiago, 25, then returned to the crash scene with the dead man strapped to the back seat and alerted authorities, prosecutors said.
The officer reportedly punched 29-year-old nurse Damian Dymka as he walked the Garden State Parkway emergency lane in the early hours of November 1.
Investigators say neither Officer Santiago nor his passenger, Albert Guzman, called 911 or rescued Mr. Dymka after he was beaten.
The men are accused of having returned to the scene of the accident several times before putting Dymka in the Honda Accord and heading home where Mr Santiago discussed what to do with his mother, Annette Santiago, and M. Guzman.
Officer Santiago then returned to the scene with his father, who is a Newark police lieutenant, and called 911.
Officials say when New Jersey State Police arrived they found Mr. Dymka dead in the back seat.
Louis Santiago has been charged with manslaughter at the wheel of a vehicle, desecration of human remains, tampering with material evidence and other counts including official misconduct.
According to the Essex County District Attorney’s Office, Mr Guzman, 25, and Ms Santiago, 53, are charged with conspiracy to desecrate human remains and obstruct arrest.
All three were arrested and released on conditions.