Over a period of three months in 2016, a small aircraft circled above the same parts of West Baltimore that so recently drew the ire of President Trump. Operated by a company called Persistent Surveillance Systems, the plane was equipped with 12 cameras which, at 8,000 feet, could take in 32 square miles of city in minute detail.

This system is an update of one originally designed for the Air Force, which was used in Iraq to provide aerial intelligence to Marines as they rolled into Fallujah, says Ross McNutt, founder and president of Persistent Surveillance Systems. Only this time, it was being used to catch criminals in the U.S.

Across 300 hours of flight time, the system captured 23 shootings, five of them fatal. In some instances, detective could use this 192-megapixel gods’-eye view to trace suspects to their getaway cars, then rewind to points when those cars had passed in front of one of the city’s 744 closed-circuit cameras.

Mr. McNutt argues that this system could reduce crime in Baltimore by up to 30%. There’s no research to back up that claim, only a 2017 review by the National Police Foundation recommending further study.

Persistent Surveillance Systems’ trial in Baltimore was only disclosed to the public two weeks after its initial phase was completed, which led to an uproar and backlash. Now, some activists and community leaders want it to come back—after all, as of 2017, Baltimore has the highest per-capita murder rate for a large city in the U.S.