What is the effect of police warning a defendant of an under-cover operation?

By contrast, in People v. Rand (1972) 23 Cal.App.3d 579, police were tipped that narcotics activity was afoot at the defendant's home. Officers surrounded the residence and telephoned the defendant with a "warning" that "'the police are coming; get rid of the stuff.'" (Id. at p. 582.) The defendant fled from the premises only to be stopped by a police officer. Questioned about narcotics, the defendant discarded a container of drugs and was placed under arrest. Citing Reeves, the defense argued the evidence should be suppressed as the product of an illegal police ruse. The appellate court disagreed: "[W]ere we to accept the defense argument . . . all under-cover activity would likewise be proscribed. Where the ruse does no more than to cause a defendant, activated by his own decision, to do an incriminating act - whether that act be a sale to an undercover agent or a jettisoning of incriminating material - no illegality exists." (Id. at p. 583; see also, State v. Hendrix (Tenn. 1989) 782 S.W.2d 833, 836 [reaching similar result on similar facts].)