Deference to police expertise happens, but as one trial court judge from New York wrote, 

Too much deference to police “expertise” is an abdication of judicial responsibility, particularly where, as here, the police officer’s own testimony shows that his expertise focuses to a disproportionate extent on Blacks and Hispanics. By the Sergeant’s own testimony, 65% to 75% of the people stopped are Black and Hispanic. They may comprise an even higher percentage of those actually arrested (and indicted). Surely this “pattern of strikes” might give rise to an inference of discrimination which requires rebuttal. Cf., People v. Jenkins, 75 N.Y.2d 550, 555 N.Y.S.2d 10, 554 N.E.2d 47 (discriminatory pattern of peremptory challenges). But the PAPD does not keep records which might rebut this inference. Thus, to the extent that the courts do not analyze the components of the so-called expertise, we may be approving of actions based on racial or ethnic bias. Cf., People v. George T., 39 N.Y.2d 1028, 387 N.Y.S.2d 247, 355 N.E.2d 302 (ethnic identity of youths on Madison Avenue created the basis of the officer’s suspicion). Minorities did not fight their way up from the back of the bus just to be routinely stopped and interrogated on their way through the terminal.                            

Anna Lvovsky has posted The Judicial Presumption of Police Expertise (Harvard Law Review, Vol. 130, Forthcoming) on SSRN.

Here is the abstract:

This Article examines the unrecognized origins and scope of the judicial presumption of police expertise: the notion that trained officers develop insight into crime sufficiently rarefied and reliable to justify deference from courts. Police expertise 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 welcomed 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.

Complicating traditional accounts of judicial deference as a largely instrumental phenomenon, this Article argues that courts in the mid-century in fact came to reappraise police work as producing rare and reliable “expert” knowledge. And it identifies at least one explanation for that shift in the folds and interconnections between courts’ diverse encounters with the police in these years. From trials to suppression hearings to professional activities outside the courtroom, judges experienced multiple sites of unique exposure to the rhetoric and evidence of the police’s expert claims. These encounters primed judges to embrace police expertise not only through their deliberative doctrinal content, but also their many structural biases toward police knowledge. This development poses important and troubling consequences for the criminal justice system, exacerbating critiques of police judgment in the Fourth Amendment context and raising novel concerns about the limits of judicial reasoning about police practices.