What is the test for establishing a conspiracy?

In order to establish a conspiracy, the prosecution must show (1) an agreement; (2) the specific intent to conspire; (3) the specific intent to commit the offense; and (4) an overt act toward the achievement of that goal. A conspiratorial agreement may be inferred from " 'the conduct of defendants in mutually carrying out a common illegal purpose, the nature of the act done, the relationship of the parties [and] the interests of the alleged conspirators . . . .' [Citation.]" (People v. Superior Court (Quinteros ) (1993) 13 Cal.App.4th 12, 20-21.) Land argues that his conspiracy conviction must be reversed because there is no evidence that he possessed the specific intent to bring controlled substances into prison. We find the evidence was more than adequate to infer Land harbored the requisite intent.