Investigating the Effects of Body-worn Police Cameras

Body worn cameras are being trialed by officers in Wolverhampton and Birmingham

Body worn cameras are being trialed by officers in Wolverhampton and Birmingham

Photo by West Midlands Police/CC BY-SA 2.0

Rates of assault against police officers are 15% higher when the officers wear cameras, possibly because they feel more confident about reporting assaults once they are captured on camera or because the officers did not keep their cameras on throughout their shift.


Police use of force is at the forefront of public awareness in many countries. Body-worn videos (BWVs) have been proposed as a new way of reducing police use of force, as well as assaults against officers. To date, only a handful of peer-reviewed randomised trials have looked at the effectiveness of BWVs, primarily focusing on use of force and complaints.

Goals & Methodology

The project team, consisting of a collaboration between the University of Cambridge, RAND Europe, and police forces in the UK and US, sought to answer the question: ‘Can BWVs reduce the use of force by and against police officers?’

In order to answer this question, the team conducted a prospective meta-analysis of 10 multi-site, multi-national randomised controlled trials with eight police forces in six jurisdictions, covering a total population of more than 2,000,000 citizens.


  • Over the ten trials, rates of assault against officers wearing cameras on their shift were an average of 15% higher, compared to shifts without cameras.
  • This could be due to officers feeling more able to report assaults once they are captured on camera — providing them the impetus and/or confidence to do so. The monitoring by camera also may make officers less assertive and more vulnerable to assault.
  • On average across all officer-hours studied, the rate of use-of-force by police on citizens was unchanged by the presence of body-worn cameras.
  • However, this varied depending on whether or not officers chose when to turn cameras on. If officers turned cameras on and off during their shift then use-of-force increased, whereas if they kept the cameras rolling for their whole shift, use-of-force decreased.

The Harvard Law Review published an article by U.S. President Barack Obama on The President’s Role in Advancing Criminal Justice Reform. In the article, President Obama cites the first paper resulting from this research project, writing, "In Rialto, California, community reports against law enforcement officers dropped nearly 88% after officers began using body-worn cameras."

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News Releases

The University of Cambridge also issued a news release on the follow-up research study.

Project Team

Barak Ariel (University of Cambridge)
Alex Sutherland (RAND Europe)
Darren Henstock (West Midlands Police)
Josh Young (Ventura, Calif., Police Department)
Paul Drover (West Midlands Police)
Jayne Sykes (West Yorkshire Police)
Simon Magicks (Cambridgeshire Constabulary)
Ryan Henderson (Police Service of Northern Ireland)