What is the test for establishing a conspiracy beyond a reasonable doubt?

People v. Earnest (1975) 53 Cal.App.3d 734 relied upon Steccone for the proposition that the "foundational requirement may be met without establishing a conspiracy beyond a reasonable doubt or even by a preponderance of the evidence; only prima facie evidence of the fact is required." (People v. Earnest, supra, 53 Cal.App.3d at p. 741.) This implies that prima facie evidence is arguably something less than a preponderance or evidence that could constitute a preponderance.