Heaggan-Brown's attorneys argued the officer had to act quickly to defend himself.
Dominique Heaggan-Brown, who also is black, was in on patrol when he and another police officer stopped two men. Smith's shooting triggered several nights of violence in Milwaukee's Sherman Park neighborhood.
Body-camera video showed Smith was unarmed and on the ground with his hands near his head when he was shot a second time in the chest, according to the criminal complaint.
Family members of a black man who was shot to death by a former Milwaukee police officer stormed out of a courtroom after the officer was acquitted in the death. Milwaukee County District Attorney John Chisholm told the jury that Smith was "in the most vulnerable position that he can possibly be in", adding that "he looks like a child", Fox6 reported.
Jurors reached their decision on the second day of deliberations in Milwaukee County Circuit Court.
Heaggan-Brown was sacked in October when he was charged with two counts of assault in a separate investigation.
Officers chased Smith on foot after he ran from a traffic stop near 44th and Auer. Not only did they acquit him on the first-degree reckless homicide charge, but they also declined to choose lesser options that included second-degree reckless homicide and homicide by negligent operation of a risky weapon.
Heaggan-Brown experienced the encounter in "real time", not in frame-by-frame motion as it was shown to the jury, Willis said, according to WTMJ.
Heaggan-Brown no longer works with the police department. As they exited their squad auto, Mr. Smith, who was armed with a handgun, darted away and ran into a yard with a chain-link fence. "The state admits that the first shot was a justified shot", defense attorney Jonathan Smith said.
Heaggan-Brown's former partner, Ndiva Malafa, testified last week they were chasing Smith, 23, because they saw he had a gun. Prosecution argued that the second shot was unnecessary because Smith had tossed his gun away by that point. They could have opted for second-degree reckless homicide or homicide by negligent operation of a unsafe weapon, but jurors acquitted Heaggan-Brown on those charges, too. The trial judge is also allowing jurors to consider two lesser charges: second-degree reckless homicide, and reckless use of a firearm.
He faces a jury trial in August in that case, in which he is accused of raping a man with whom he had been drinking.
But Heaggan-Brown's attorneys say he feared for his safety and had to make a split-second decision.