USCourts.GOV

It is not enough, however, that they simply met, discussed matters of common interest, acted in similar ways, or perhaps helped one another. You must find that there was a plan to commit at least one of the crimes alleged in the indictment as an object of the conspiracy with all of you agreeing as to the particular crime which the conspirators agreed to commit.

On the other hand, one who has no knowledge of a conspiracy, but happens to act in a way which furthers some object or purpose of the conspiracy, does not thereby become a conspirator. Similarly, a person does not become a conspirator merely by associating with one or more persons who are conspirators, nor merely by knowing that a conspiracy exists.