More than 22,000 police officers in London will be issued body cameras by summer 2017. The wide-scale deployment of the devices follows years of trials and evaluations, with the UK's police force claiming that the cameras will help deliver "speedier justice for victims."

The cameras are built by Taser, worn on the front of an officer's uniform, and activated manually. Police have to inform members of the public when they turn the camera on "as soon as practical," with a red light on the front of the device turning on when in use. When returned to its charging dock, the camera automatically uploads its footage to a police server. If police don't expressly ask to retain the footage for evidence then it's deleted in 31 days. Anyone can request to see footage taken of them by the cameras under data protection laws.

"People are more likely to plead guilty when they know we have captured the incident."

"What we do every day will be seen by the public — that has to be good!" said Metropolitan Police Commissioner Sir Bernard Hogan-Howe in a press statement. "Our experience of using cameras already shows that people are more likely to plead guilty when they know we have captured the incident on a camera. That then speeds up justice, puts offenders behind bars more quickly and most importantly protects potential victims."

The effect of body cameras on policing is a complex issue though, and the full scope of the technology's benefits and dangers are as yet unknown. In the UK, police say the cameras are particularly useful for prosecuting domestic abuse cases, with offenders more likely to plead guilty when they know they've been recorded. By some metrics, the cameras also moderate police behavior, with a recent year-long study looking at officers in the US and UK finding complaints against police fell by 93 percent after the deployment of the technology.

In the US it's been hoped that body cameras could help increase accountability and heal public trust over the killings of unarmed black men. However, in a number of cases — such as the killing of 31-year-old Terrence Sterling in September — body cameras were only activated after shots were fired. Incidents like this combined with the patchwork of rules governing who gets to see camera footage usage has led to civil rights groups criticizing the technology, arguing that it gives more power to law enforcement than to citizens.

Body cameras continue to be embraced by police departments on both sides of the Atlantic though, and last month, the Department of Justice announced $20 million in additional funding for the technology. "Effective public safety requires more than arrests and prosecutions," said Attorney General Loretta Lynch in a statement. "It also requires winning — and keeping — the trust and confidence of the citizens we serve."