Research Question <p>Can research discover the true cost-effectiveness of new technologies in policing, such as automatic license plate readers (ALPR)?</p> Data <p>We review the findings of many impact tests of introducing ALPR readers in predominantly US police agencies.</p> Methods <p>We place the data in the context of the two key police mandates: public safety and public confidence. We then apply the logic of linking findings specific to the new technology with the two broad mandates.</p> Findings <p>The effect of any technology on police outcomes depends heavily on how it is implemented in the larger context of organizational systems and culture. The effect is also conditioned by a broad body of evidence that the key mandates depend on far broader foundations than on any specific technology.</p> Conclusions <p>Evidence-based policing cannot be built from isolated findings, such as marginal changes in outputs or outcomes associated with new technologies. Linking new technologies to joined-up systems of targeting, testing, and tracking is required before we can ask whether the technologies are cost-effective.</p>