DESPITE THE EXISTING SUBSTANTIAL BODY OF JUDICIAL DECISIONS DEFINING STANDARDS OF POLICE CONDUCT, RELIABLE EVIDENCE ON POLICE COMPLIANCE IS NOT READILY AVAILABLE. POLICE OFFICERS' REPORTS ON THEIR OWN BEHAVIOR ARE OBVIOUSLY BIASED; THEREFORE, DIRECT OBSERVATION MUST BE CONSIDERED A MORE REALISTIC METHOD OF EVALUATING COMPLIANCE. THE MIRANDA RIGHTS AND THE EXCLUSIONARY RULE ARE THE BEST KNOWN EXAMPLES OF COURT DECISIONS TO IMPOSE LEGAL LIMITATIONS ON POLICE DISCRETION. THE COMPLIANCE FACTORS BY WHICH THE EFFECTIVENESS OF COURT DECISIONS ON THE PRACTICES OF REGULATORY AGENCIES CAN BE ASSESSED ARE (1) THE LIKELIHOOD THAT NONCOMPLIANCE WILL BE CHALLENGED IN THE COURTS; (2) THE SYMPATHY OF JUDGES TOWARD THESE CHALLENGES; AND (3) THE IMPACT THAT SUCCESSFUL CHALLENGES MAY HAVE ON THE ADMINISTRATION INVOLVED (IN THIS CASE, POLICE DEPARTMENTS). INCENTIVES TO COMPLY ARE THE DANGER THAT POLICE VIOLATIONS OF THE EXCLUSIONARY RULE MAY ENDANGER CONVICTIONS, AND THE IMPORTANCE TO POLICE OFFICERS OF OBTAINING CONVICTIONS. THE FIRST INCENTIVE IS WEAKENED BY THE FACT THAT EVIDENCE OBTAINED THROUGH AN ILLEGAL SEARCH COULD NOT HAVE BEEN OBTAINED OTHERWISE, SO THAT WITHOUT IT THERE WOULD BE NO CASE IN THE FIRST PLACE. THE SECOND INCENTIVE IS EVEN WEAKER, BECAUSE POLICE OFFICERS, DESPITE THEIR NATURAL DESIRE TO SEE CRIMINALS CONVICTED, ARE MORE INTERESTED IN ARRESTS. ARREST FIGURES ARE THE QUANTIFIED INDEX OF THEIR PERFORMANCE FOR REWARDS AND PROMOTIONS. THIS STUDY FINDS THAT POLICE OFFICERS TRY TO MAINTAIN THEIR DISCRETION, DESPITE THE EXCLUSIONARY RULE AND THE MIRANDA RIGHTS. THE LATTER IS EASIER TO RECONCILE WITH POLICE EFFECTIVENESS. POLICE OFFICERS HAVE GREATER DIFFICULTIES WITH THE EXCLUSIONARY RULE, TO THE EXTENT OF RESORTING TO PERJURY IN COURT IN ORDER TO HIDE THE CIRCUMSTANCES UNDER WHICH THE EVIDENCE WAS OBTAINED. THERE HAS BEEN SOME PRESSURE TO ABOLISH THE EXCLUSIONARY RULE BECAUSE OF FAILURE TO COMPLY BY THE MAJORITY OF POLICE OFFICERS AFFECTED BY IT. HOWEVER, THERE IS NOT ENOUGH EVIDENCE OF THIS FAILURE TO WARRANT ITS ELIMINATION. FOOTNOTES ARE APPENDED. (LGR)