From interview with David Simon (Where the Baltimore Police Went Wrong):

The documented litany of police violence is now out in the open. There’s an actual theme here that’s being made evident by the digital revolution. It used to be our word against yours. It used to be said—correctly—that the patrolman on the beat on any American police force was the last perfect tyranny. Absent a herd of reliable witnesses, there were things he could do to deny you your freedom or kick your ass that were between him, you, and the street. The smartphone with its small, digital camera, is a revolution in civil liberties.