When NFL player Ryan Moats was pulled over by a Dallas police officer earlier this month, the incident could have turned into a "he-said-he-said" situation.
But because Officer Robert Powell had a dashboard-mounted camera in his car, the 13-minute harangue of Moats, who pleaded with the rookie officer to let him get to his dying mother-in-law's bedside, was recorded from start to finish.
The video, which police released last week, has hit the Internet and sparked nationwide outrage. Police Chief David Kunkle has been bombarded with calls to fire Powell, who is on leave.
In a statement released by his lawyer, Powell said the incident was "unfortunate."
But while Powell's taped diatribe may prove to be a career ender, experts say the in-car video can just as often save a career threatened by bogus misconduct claims.
In-car cameras and video from bystanders have "had a huge impact in being able to provide independent visual documentation of the incident," said Sam Walker, a national police accountability expert, in Sunday's editions of The Dallas Morning News.
"If the officer did the right thing, then it's good for us to know that and have some independent documentation," he said. "If the officer was in the wrong, then it's good for us to know that. This is what's been lacking in most police use-of-force incidents. Traditionally, you would have had a he said-he said situation. As the cliché has always been, the tie goes to the officer."
The infamous Rodney King beating by Los Angeles police officers 18 years ago solidified the power of video, for the officers and suspects.
In Moats' case a Plano officer also witnessed part of the traffic stop and reported it to his supervisors. But without the video, an internal affairs probe may have stalled.
"It would have been their word against (Powell), and it probably would have ended up being inconclusive," said Assistant Chief Floyd Simpson, who oversees the city's seven patrol stations. "The in-car camera systems bring a different view."
In Dallas, about 67 percent of the department's 906 squad cars have one of the $4,400 cameras, said Lt. Dale Barnard, the department's fleet coordinator.
The camera begins recording automatically when an officer flips on lights and sirens, or if the patrol car is in a crash. Officers are required to wear microphones to record conversations. It is against DPD rules for an officer to turn off the camera, and officers cannot erase the videos.
Videos that need to be kept as evidence or for longer than 90 days are reviewed by a sergeant.
According to the federal Bureau of Justice Statistics, as of 2003, 54 percent of police departments in cities with more than 250,000 people use in-car cameras.
In Dallas, the cameras have proved to be a mixed bag for local officers.
In August, two Dallas police officers arrested a drunken man at a club near a southwest patrol substation. The man later complained that the officers had roughed him up, but the officers were cleared when investigators heard an audio recording showing that the man was yelling, screaming and kicking the cage in the squad car.
Cameras also led to several reprimands after a Sept. 6 chase.
A Dallas police video also showed the Oct. 17 death of 10-year-old Cole Berardi, who was struck by an officer driving at least 29 mph over the speed limit on a dark road without sirens or emergency lights.
That video helped persuade Kunkle to issue new driving guidelines requiring that officers not drive above the speed limit unless lights and sirens are activated.
In Oakland, Calif., New Year's Day cell phone videos showed a 27-year-old transit police officer shooting Oscar Grant, 22, who was being detained along with several other young black men while police investigated a fight on a train.
The officer is facing murder charges.