He clicked “INVESTIGATE,” and Citigraf got to work on the reported assault. The software runs on what Genetec calls a “correlation engine,” a suite of algorithms that trawl through a city’s historical police records and live sensor feeds, looking for patterns and connections. Seconds later, a long list of possible leads appeared onscreen, including a lineup of individuals previously arrested in the neighborhood for violent crimes, the home addresses of parolees living nearby, a catalog of similar recent 911 calls, photographs and license plate numbers of vehicles that had been detected speeding away from the scene, and video feeds from any cameras that might have picked up evidence of the crime itself, including those mounted on passing buses and trains. More than enough information, in other words, for an officer to respond to that original 911 call with a nearly telepathic sense of what has just unfolded.