Does the exclusionary rule apply to cases such as the one at bar in which the purpose of the police activity is neither the prosecution nor prevention of crime?

[16 Cal.3d 262] The exclusionary rule should be subject to reasonable restrictions, one of which, in my view, should limit the rule to its correct regulatory role. It should not apply to cases such as the one at bar in which the purpose of the police activity is neither the prosecution nor prevention of crime. This limitation may, on occasion, raise difficult problems of proof, but this difficulty is a common one in the law (see, e.g., People v. Brisendine, supra, 13 Cal.3d 528 at pp. 534--535, 119 Cal.Rptr. 315, 531 P.2d 1099) and is not so acute as to require automatic application of an overbroad rule, the effect of which tends to sacrifice other important societal interests.