Transcript for Officer Defends His Actions in Walter Scott Murder Trial
and to a stunning moment in court today. In South Carolina, officer Michael Slager taking the stand in his own defense, charged in the shooting death of driver Walter Scott, after a routine traffic stop. Here's ABC's Steve osunsami. I made the decision to use lethal force, because Mr. Scott never stopped. Reporter: This former police officer took a giant risk testifying. Michael Slager looked into the jury's eyes and told them that at this very moment, when he started firing at Walter Scott in the green shirt, he felt afraid for his life. I fired until the threat was stopped, like I'm trained to do. Reporter: Scott was unarmed, and is clearly seen in this cell phone video running away. Prosecutors say it was murder, and made Slager stand up and hold a tape ruler to show jurors how far Scott ran. A whole 18 feet before Slager started shooting. Slager is claiming that Scott grabbed his taser in a fight before the cell phone recording. And I saw that taser coming at me, coming at me like this. Reporter: But he now admits that Scott didn't run away holding it. People in the courtroom shook their heads as Slager struggled to explain this -- why he picked up the taser from this location and moved it closer to Scott's dead body. Was it because I was policing my gear? I can't even answer to that. Reporter: Slager told jurors he wasn't trying to plant evidence. But outside this courthouse, in the black neighborhoods where he once worked, they don't believe him. David? Steve, thank you.
This transcript has been automatically generated and may not be 100% accurate.