In a column last December, I noted that video footage, while not necessarily decisive in cases where police use deadly force, can make a crucial difference. Here is a good example: Today police in North Charleston, South Carolina, arrested one of their own, Patrolman Michael Slager, and charged him with murder in the shooting death on Saturday of a motorist named Walter Scott. Slager initially claimed, through an attorney, that he feared for his safety after Scott grabbed his Taser during a struggle. But a bystander shot video that shows Slager firing eight rounds at a fleeing Scott, striking him in the back.

"When you're wrong, you're wrong," North Charleston Mayor Keith Summey said after viewing the recording. "When you make a bad decision, don't care if you're behind the shield or a citizen on the street, you have to live with that decision."

Slager, who is 33 and white, pulled over Scott, who was 50 and black, on Saturday morning near the intersection of Remount and Craig roads because the Mercedes-Benz sedan Scott was driving had a broken brake light. Scott took off on foot, apparently because he had an outstanding warrant for failure to pay child support. Slager pursued him on foot and, according to a statement the patrolman made through his lawyer earlier this week, drew his Taser in an attempt to subdue Scott, who grabbed the weapon, at which point Slager "felt threatened." In the the three-minute video, which shows the end of the chase and the immediate aftermath, Scott is not menacing Slager but is instead running away as the officer fires his weapon.

In the 1985 case Tennessee v. Garner, the Supreme Court said the Fourth Amendment allows police to shoot at a fleeing suspect only when he "poses a threat of serious physical harm, either to the officer or to others." It seems unlikely that Scott, a nonviolent offender who was armed at most with a weapon that is supposed to be nonlethal, fit that description. But in the absence of the video, Slager's version of events, which was initially the official police account, might have been accepted.

Two state legislators from the Charleston area say the shooting shows the need to move forward with a bill that would require police officers to wear body cameras. "My goal is to try to utilize modern-day technology to cut through the rumors and the lies when it comes to these unfortunate incidents," Rep. Wendell Gilliard (D-Charleston) told the Charleston Post and Courier. "Cameras don't lie."

Ron Bailey has more on police body cameras here.