What is the test for establishing there was a conspiracy?

Whether a conspiracy exists, however, is a preliminary question which must be proved by a preponderance of the evidence. Bourjaily v. United States, 483 U.S. 171, 175-76 (1987). In making this preliminary determination, a trial court is free to examine the putative hearsay statements of a coconspirator; i.e., the court is not obligated to look only at independent evidence in support of a showing that a conspiracy existed. Id. at 181; United States v. Layton, 855 F.2d 1388, 1401 (9th Cir.1988), cert. denied, 109 S.Ct. 1178 (1989).