https://news.vice.com/article/reports-suggest-body-cameras-are-only-effective-when-cops-cant-turn-them-off
"Oakland has experienced a significant decrease in use of force by police since cameras were introduced five years ago. In 2009, before the cameras were put into action, Oakland cops racked up 2,186 use-of-force incidents. In 2013, when around 500 officers wore cameras, there were 836 cases involving force. By the end of 2014, 619 officers were outfitted with cameras and the city was down to 572 use-of-force incidents."