INTRODUCTION Covert policing necessarily involves deception, which in turn often leads to participation in activity that appears to be criminal. In undercover operations, the police have introduced drugs into prison, (1) undertaken assignments from Latin American drug cartels to launder money, (2) established fencing businesses that paid cash for stolen goods and for "referrals," (3) printed counterfeit bills, (4) and committed perjury, (5) to cite a few examples. (6)