The former North Charleston, S.C., police officer charged with murder in the death of an unarmed black man during a traffic stop took the stand Tuesday to testify in his own defense.

Michael Slager is accused of gunning down Walter Scott after pulling him over for a broken taillight. If convicted, Slager could face life in prison.

The April 2015 incident was captured on two videos — one from Slager's dashcam showing the traffic stop and a second recorded by a bystander using a cellphone that showed the shooting.

As NPR's Debbie Elliott has reported, "Video from Slager's dashcam shows the officer at the driver's window, asking for Scott's driver's license and questioning him about documents for the car. After Slager returns to his patrol car, Scott jumps out of the car and runs. Slager gives chase, and there's an off-camera confrontation."

The cellphone video shows Scott running away in an empty lot when Slager fires eight rounds and shoots him in the back.

Once the bystander video was made public, the North Charleston Police Department fired Slager and a grand jury indicted him on murder charges.

On Tuesday, Slager emphasized that he had acted according to his training as a police officer, and that he had been afraid of Scott. He contended, as he has previously, that Scott had taken his Taser stun gun.

He also said Scott had "grabbed a bat — a bat or a club" from the car as Slager and another officer pulled him out of the vehicle.

Slager said he chased Scott because he "must have been running for a certain reason." He testified that as he tried to handcuff Scott, Scott grabbed his Taser. Slager's voice cracked as he said he had been "in total fear."

"I saw that Taser coming at me," he said. "I fired until the threat was stopped, like I'm trained to do."

Slager's defense attorney asked him at one point whether Scott had insulted police officers using an expletive during the altercation. Slager said yes.

With Slager on the witness stand, the prosecution played the bystander video for the court. No bat, club or Taser is visible in the grainy footage.

During cross-examination, Slager repeatedly said he could not remember details of his thoughts or actions during the moments captured on the video.

"My family's been destroyed by this. [Walter] Scott's family has been destroyed by this," Slager said as he ended nearly two hours of testimony. "It's horrible."

Slager, who is white, is also facing separate federal civil rights charges over Scott's death. In that indictment, federal prosecutors accuse Slager of deliberately misleading investigators by telling them he had fired his weapon "while Scott was coming forward at him with a Taser."

"In truth and in fact," the indictment reads, "as defendant MICHAEL SLAGER then well knew, he (SLAGER) repeatedly fired his weapon at Scott as Scott was running away from him."

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