The day before Halloween in 2012, Donnie Fowler, a lobbyist from a little-known tech start-up called PredPol, e-mailed a confidential login and password to the San Francisco Police Department's chief information officer, Susan Merritt. The password allowed Merritt to log into an online mapping tool that, according to Fowler and his business partners, was already predicting where crimes are likely to happen across San Francisco. Fowler was, if his company is to be believed, giving the SFPD the keys to the next generation of crime-fighting, a program that draws from the past to help police, presumably, change the future. PredPol...