All SEPTA Police Department officers will soon be equipped with body cameras that will offer a new layer of protection to police and customers, the agency's chief said Friday.

"I like to say, cameras are going to make good cops great cops, and make the rest of them follow the rules," Chief Thomas Nestel III said during a news conference.

Most of the department's 289 officers already have body cameras, the chief said, and the remainder will be equipped with them in coming days.

The department spent about $300,000 on the cameras and an additional $100,000 on training, the agency said. SEPTA police began testing the cameras in July 2014, and the board of directors approved their use throughout the department a year later.

Only one of the Philadelphia Police Department's 23 districts, the North Philadelphia-based 22d District, has body cameras assigned to its officers.

During the news conference, Nestel showed three videos taken from body cameras used in the department's pilot program.

One of the videos showed a male suspect with his hands cuffed behind his back banging his head against a side window of a SEPTA police car.

The video became significant when a person in the area overheard the man shouting, and reported an incident of police mistreatment of a suspect. The video was instrumental in proving that officers were not touching the man when he injured himself.

"What's useful to us is to have another piece of evidence to point to to show we were wrong or we were right," Nestel said.

In purchasing cameras, Nestel said, he had two priorities. He wanted a camera that, if dislodged during a physical altercation, could not be picked up by anyone and used. The cameras purchased will disconnect from the data storage element if they are pulled off an officer. He also thought it was important that officers could not review video before writing their reports.

"Administratively, we control who has access," he said.

jlaughlin@phillynews.com

215-854-4587 @jasmlaughlin