Police departments across the world should require the use of body-worn video cameras for their officers. Research has shown that filming police public interactions can lower levels of violence within these encounters because the known presence of the camera encourages police officers to better regulate their own behaviour. While it is now common for bystanders to capture footage of police public encounters on their camera phones or similar devices, police implementation of body-worn video cameras is preferable for a number of reasons. Chief amongst these reasons is the fact that police procedures for body-worn cameras require that an officer issue a clear warning from the start that everyone in an interaction is being filmed.