Just 10 days after the shooting on July 19, 2015, Mr. Deters charged Mr. Tensing with murder and voluntary manslaughter, and released body camera footage that showed a routine traffic stop devolve into violence in a matter of seconds.

In the footage, Mr. Tensing is seen pulling over a green Honda Accord because, the officer says, of a missing front license plate. Despite requests from Mr. Tensing, Mr. DuBose does not produce a driver’s license. Mr. Tensing asks Mr. DuBose to remove his seatbelt and places his hand on the car door, to open it. Then, as the footage turns shaky, Mr. DuBose closes the door with one hand and starts the car with his other hand. Mr. Tensing reaches into the car and yells “Stop!” twice, the video shows, at which point the officer fires his gun once, striking Mr. DuBose in the head.

Prosecutors said that Mr. Tensing shot to kill and that Mr. DuBose was not a threat. Mr. Tensing, who took the stand in his own defense during both of his trials, said he believed his arm was caught in the steering wheel — an assertion prosecutors used the video to challenge — and that he shot “to stop the threat” because he thought he was going to be dragged by Mr. DuBose in his car.

Mr. Tensing’s first trial ended in a mistrial. After Mr. Deters said his office would prosecute the case a second time, more complications emerged. Some evidence from the first trial, including the T-shirt showing the Confederate battle flag that Mr. Tensing was wearing underneath his uniform, was not admitted at the second trial. Halfway through, prosecutors tried to add a lesser charge of reckless homicide, but Judge Leslie Ghiz concluded that it was too late. That trial ended last month, with a jury that said it was almost evenly split.

On Tuesday, when asked about the role race played in the jurors’ deliberations, Mr. Deters seemed to suggest that his jury pools were not immune to the sharp differences in the way people view the use of force by the police.