THE DECISION IN KATZ VERSUS THE UNITED STATES, HOLDING THAT THE FOURTH AMENDMENT PROTECTS PEOPLE NOT PLACES, HAS INCREASED THE NEED FOR ANTECEDENT JUSTIFICATION AND PROBABLE CAUSE IN ALL MANNER OF POLICE INVESTIGATIVE PROCEDURES WHICH DO NOT FIT THE CLASSICAL DEFINITIONS OF SEARCH AND SEIZURE. THE PRIMARY USE OF BUMPER BEEPERS HAS BEEN BY POLICE INTELLIGENCE, TO TRACK THE MOVEMENT OF A SUSPECT OR TO SUPPLEMENT VISUAL SURVEILLANCE. THE FIRST OF THE BEEPER CASES DID NOT ARISE UNTIL 1975, WHEN AN ATTEMPT WAS MADE TO SUPPRESS EVIDENCE OBTAINED WITH THE AID OF A BEEPER IN A NARCOTICS CASE. THE COURT DECIDED THAT THE BEEPER INFRINGED ON EXPECTATIONS OF PRIVACY AND THAT ANY DECISION TO IMPLANT A BEEPER REGARDING THE AMOUNT OF INTRUSION AND THE EXPECTATION OF PRIVACY SHOULD BE MADE BY A MAGISTRATE AND NOT BY THE AGENTS. THIS DECISION WAS OVERTURNED BY THE NINTH CIRCUIT COURT OF APPEALS IN 1976, WHICH RULED THAT SO LONG AS NO FOURTH AMENDMENT RIGHTS HAD BEEN VIOLATED WHEN THE BEEPER WAS ATTACHED (E.G., A WARRANT WAS OBTAINED), THERE SHOULD BE NO DISTINCTION BETWEEN VISUAL SURVEILLANCE AND THE USE OF A BEEPER. FURTHER DECISIONS HAVE SUPPORTED THE WARRANTED USE OF BEEPERS IN CASES WHERE PROBABLE CAUSE FOR SEARCH AND SEIZURE EXISTED, AND HAVE TAKEN INTO ACCOUNT THE REASONABLE EXPECTATION OF PRIVACY IN A GIVEN SITUATION. ADDITIONAL PROBLEMS IN THE USE OF BUMPER BEEPERS WHICH COULD ARISE IN FUTURE CASES INCLUDE THE FACT THAT FEDERAL COMMUNICATIONS COMMISSION RULES DO NOT AFFIRMATIVELY AUTHORIZE BEEPER OPERATION ON ANY PUBLIC SAFETY FREQUENCY, AND NO STATE STATUTE CONTAINS AFFIRMATIVE LANGUAGE PERMITTING JUDICIALLY AUTHORIZED BEEPER ORDERS. IN ITS FINAL REPORT, THE NATIONAL WIRETAP COMMISSION CONCLUDED THAT THE STATE OF THE LAW ON BUMPER BEEPERS WAS FAR FROM CLEAR AND RECOMMENDED STATUTORY CLARIFICATION OF THE PROCEDURES TO BE FOLLOWED IN THEIR UTILIZATION. IT IS CONCLUDED THAT THE BEEPER IS A WORTHWHILE INVESTIGATIVE AID, BUT POLICE USE SHOULD BE SUBJECT TO PROPER LEGAL CONTROLS. (JAP)