IN June, a father of six was shot dead on a Monday afternoon in Evanston, Illinois, a suburb 10 miles north of Chicago. The Evanston police believe that the victim, Ray C. Owens, had also been robbed. There were no witnesses to his killing, and no surveillance footage either.
With a killer on the loose and few leads at their disposal, investigators in Cook County, which includes Evanston, were encouraged when they found two smartphones alongside the body of the deceased: one running on Apple’s iOS 8 operating system, and another on Google’s Android operating system. Both devices were passcode protected.