What is the test for establishing an agency relationship between an informant and a jailhouse inmate?

Where the informant is a jailhouse inmate, the first prong of the foregoing test is not met where law enforcement officials merely accept information elicited by the informant-inmate on his or her own initiative, with no official promises, encouragement, or guidance. (People v. Gonzalez (1990) 51 Cal.3d 1179, 1240, 275 Cal.Rptr. 729, 800 P.2d 1159.) In order for there to be a preexisting arrangement, however, it need not be explicit or formal, but may be "inferred from evidence that the parties behaved as though there were an agreement between them, following a particular course of conduct" over a period of time. (U.S. v. York, supra, 933 F.2d at p. 1357.) Circumstances probative of an agency relationship include the government's having directed the informant to focus upon a specific person, such as a cellmate, or having instructed the informant as to the specific type of information sought by the government. (Id., at p. 1356.)