But tapes were used for far more than learning, said Meehan. As in-car cameras began to proliferate in the late 1990s, he said that he noticed cops would begin to hold onto audio and video recordings of their stops. But not just their own: Officers were building personal libraries of notable audio and video recordings. To Meehan, the sociologist, police officers were augmenting what had been a mostly unwritten cop culture, full of dishy stories of terrible stops, with AV.

“Officers were using technology to supplement their stories, and reinforcing certain stereotypes about police,” Meehan told me. He found cops who had built libraries of tapes that depicted their work as dangerous, funny, or horror-filled. But he also found cops whose libraries “reinforced negative stereotypes” about policing.

That is: Their libraries were racist. “There was an officer holding dispatch tapes from the 1967 Detroit riots,” Meehan told me. “I thought that was notable. This was the late 1990s, so those tapes had floated around for 30 years.”

Video—especially digital video—is slippery. If cops have body cams, they’ll get personal access to the videos they record. And then they can view them whenever they want.