The statement that a declaration is admissible against a coconspirator without establishing the conspiracy "even by a preponderance of the evidence" for the purposes of Evidence Code section 1223 has often been repeated since People v. Earnest, supra, 53 Cal. App. 3d 734. (See People v. Longines (1995) 34 Cal. App. 4th 621, 626 40 Cal. Rptr. 2d 356; People v. Jeffery, supra, 37 Cal. App. 4th 209, 215; People v. Olivencia (1988) 204 Cal. App. 3d 1391, 1402-1403 251 Cal. Rptr. 880; People v. Lipinski (1976) 65 Cal. App. 3d 566, 575 135 Cal. Rptr. 451.) Although these cases discuss the circumstantial evidence of their respective conspiracies in terms of a prima facie case, they generally do not discuss whether the circumstantial evidence is sufficient for the trier of fact, the jury, to sustain a finding of conspiracy. This is misleading because the prima facie showing of a conspiracy is in fact evidence sufficient to sustain a finding of fact of a conspiracy by a preponderance of the evidence. (Evid. Code, 1223, subd. (c); People v. Von Villas (1992) 11 Cal. App. 4th 175, 231 15 Cal. Rptr. 2d 112, citing 1 Jefferson, Cal. Evidence Benchbook (Cont.Ed.Bar 2d ed. 1982) 3.5.) The question becomes whether there is sufficient evidence which, if believed by the jury, would support the finding of a conspiracy. "The court should exclude the proffered evidence only if the 'showing of preliminary facts is too weak to support a favorable determination by the jury'." (People v. Lucas (1995) 12 Cal. 4th 415, 466 48 Cal. Rptr. 2d 525, 907 P.2d 373, citing 3 Witkin, Cal. Evidence (3d ed. 1986) Introduction of Evidence at Trial, 1716, p. 1675; see Evid. Code, 403, subd. (a); People v. Simon, supra, 184 Cal. App. 3d at p. 131.) "The decision whether the foundational evidence is sufficiently substantial is a matter within the court's discretion." (People v. Lucas, supra, 12 Cal. 4th at p. 466, citing Alvarado v. Anderson (1959) 175 Cal. App. 2d 166, 178 346 P.2d 73.) The trial court has the preliminary, but not the final, authority to determine the question of the existence of the preliminary fact. Unlike in other situations under Evidence Code section 403, 'the preliminary fact questions listed in subdivision (a) of Evidence Code section 403 . . are not finally decided by the judge because they have been traditionally regarded as jury questions. The questions involve the credibility of testimony or the probative value of evidence that is admitted on the ultimate issues. It is the jury's function to determine the effect and value of the evidence addressed to it. . . . the judge's function on questions of this sort is merely to determine whether there is evidence sufficient to permit a jury to decide the question. The "question of admissibility . . . merges imperceptibly into the weight of the evidence, if admitted." (People v. Lucas, supra, 12 Cal. 4th at pp. 466-467, citing Legis. Com. com., 29B pt. 1 West's Ann. Evid. Code (1995 ed.) foll. 403, p. 361.)