Abstract: We take two professions — police officers and doctors — and place their experiences with big data in dialogue. Policing and medicine, while naturally different in some obvious respects, actually both need to grapple with a lot of the same moral, social, and legal questions that come with adopting big data programs. This because, as we discuss below, both professions generally possess a monopoly over an acute societal vulnerability, be it safety or health, and have accordingly developed a set of settled internal norms to shape individual discretion in service of each respective function. We place the professions side-by-side and try to distill certain insights from the perspective of three key stakeholders — practitioners, policymakers, and the polity.