California Code, Probate Code - PROB § 249

At any time before the hearing any person interested in the property may answer the petition and deny any of the matters contained therein. The court shall hear the proofs offered by the petitioner and by any person contesting and shall make a decree conformable to the proofs. The decree shall be prima facie evidence of the facts determined thereby, and shall be conclusive in favor of anyone acting thereon in good faith without notice of any conflicting interest.