Drone attacks by the United States have killed hundreds of civilians, according to a new study by the human-rights organization Reprieve.

The Guardian reports that: “Reprieve, sifting through reports compiled by the Bureau of Investigative Journalism, examined cases in which specific people were targeted by drones multiple times. Their data, shared with the Guardian, raises questions about the accuracy of US intelligence guiding strikes that US officials describe using words like ‘clinical’ and ‘precise.'”

In studying the multiple drone attacks on 41 specific targets, Reprieve found that “Attempts to kill 41 men resulted in the deaths of an estimated 1,147 people, as of 24 November,” according to The Guardian. This data confirms previous reports of the shocking level of “collateral damage” being inflicted by U.S. drone strikes.

The lead research for the Reprieve study concludes that “Drone strikes have been sold to the American public on the claim that they’re ‘precise’. But they are only as precise as the intelligence that feeds them.”

The Guardian reports on the U.S. drone attacks.