Tulsa officer Betty Shelby killed 40-year-old Terence Crutcher on 16 September in a confrontation caught on video. Betty Shelby could face between four years and life in prison if convicted of the 2016 manslaughter that killed Terence Crutcher.
Shelby has said she shot Crutcher when he reached into his auto window because she thought he was going for a gun.
An autopsy showed Mr Crutcher did have PCP in his system, and police said they found a vial of it in his SUV.
"If you hesitate and delay, then you die", Shelby said.
Crutcher's twin sister, Tiffany Crutcher, said her brother's hands were up, that he was not an imminent threat or attack her and didn't deserve to be shot.
At one point, Gray asked: "Is Terence Crutcher's death his fault?" Shelby told the jury, "I did everything I could to stop this".
Following Shelby's acquittal, protesters gathered outside the Tulsa County Courthouse holding signs and shouting "No justice, no peace, no racist police".More news: USA officials warn Trump against moving U.S. embassy to Jerusalem
The jury got the case shortly after noon Wednesday.
Betty Shelby, the Tulsa police officer who fatally shot an unarmed black man previous year, was found not guilty of first-degree manslaughter by a jury late Wednesday. Video footage of the incident showed him being shot as he had his hands in the air.
In this September 16, 2016, image made from video provided by police, Terence Crutcher, left, with his arms held up, is pursued by police officers as he walks next to his stalled SUV moments before he was shot and killed by one of the officers in Tulsa, Oklahoma.
Assistant District Attorney Kevin Gray argued that even if Shelby followed her police training, which taught her that "action beats reaction", it doesn't mean she didn't commit a crime.
District Attorney Steve Kunzweiler spent just more than an hour restating the state's case, telling jurors have every reason to look at the evidence and ask why: Why officers responding to the shooting didn't immediately ask what happened. She acknowledge it was an important detail, but she said she had forgotten.
"In spite of anything that Terence may have done in his past that may have a negative turn to it, it does not justify murder", he said.
But Benjamin Crump, an attorney representing the Crutcher family, said Crutcher's window was rolled up, making it unlikely he was reaching into the auto. "She didn't know about anything in his past when she murdered him". Jeanne MacKenzie, Tulsa police spokeswoman, claimed the officers believed he began to reach into his vehicle. She said she "thought he [Crutcher] had a gun" because he repeatedly put his hands in and out of his pockets and reached inside of his vehicle window.
Drummond refused the request and later told jurors to return Wednesday for closing arguments. She called the decision to charge Shelby a "small victory".