Anna Lvovsky
This Article examines the unrecognized origins and scope of the judicial presumption of police expertise: the notion that trained, experienced officers develop insight into crime sufficiently rarefied and reliable to justify deference from courts. That presumption has been widely criticized in Fourth Amendment analysis. Yet the Fourth Amendment is in fact part of a much broader constellation of deference, one that begins outside criminal procedure and continues past it. Drawing on judicial opinions, appellate records, trial transcripts, police periodicals, and other archival materials, this Article argues that courts in the mid-twentieth century invoked police expertise to expand police authority in multiple areas of the law. They certified policemen as expert witnesses on criminal habits; they deferred to police insights in evaluating arrests and authorizing investigatory stops; and they even credited police knowledge in upholding criminal laws challenged for vagueness, offering the officer’s trained judgment as a check against the risk of arbitrary enforcement.