’Jim Thatcher, an urban studies professor at the University of Washington, Tacoma, is skeptical. “If you give people this power to draw attention based around a dangerous event,” Thatcher says, “then they are actually encouraged to seek out, or at worst manufacture, these dangerous events,” noting the speed with which Citizen escalated the manhunt. Like many others, Thatcher downloaded Citizen during last year’s protests. He wondered whether it might be used as a tool for “sousv...