GENEVA, SWITZERLAND —   Growing use of body cameras by police has led to a dramatic fall in brutality, a top UN rights expert said Friday, but warned the technology could be a double-edged sword.

There have been increasing calls for police to wear body cameras following a spate of cases, especially in the United States, of police violence and killings of unarmed people caught on camera.

“It seems from some of the early studies that … up to 60 percent of the use of force (is) reduced when police wear body cameras,” UN Special Rapporteur Christof Heyns told a briefing. (emphasis added)

He said complaints of the use of excessive force had meanwhile declined by 90 percent, according to the studies. There was as well a marked decrease in what he called the ‘trigger happy’ approach.

Heyns, who in 2011 spearheaded moves to authenticate a five-minute video clip showing atrocities in Sri Lanka during the government’s war against Tamil separatists, however said that new technology had led to a ‘digital divide’ with unfilmed violations risking being ignored.

“A mindset may arise that unless a body camera was used, the police or the courts […]