Can an algorithm predict crime? For several years, United States police forces have used software that is said to detect the locations of future crimes and offences. Of the many companies working in this field, Predpol is the name that is mentioned the most. But the success of this Californian start-up is more the result of marketing than any actual predictive effectiveness. The stance of this paper is twofold: first, a closer look from the seismologist who developed the algorithm reveals that this solution is far from having the predictive capacity boasted by its promoters. Second, the ethical problem with Predpol’s algorithm appears not to be police discrimination, as many feared, but rather the exclusion of a section of the population from the public security offering.