What is the legal test for establishing beyond a reasonable doubt in a sexual assault case?

Constitution. [Citation.] "In determining whether a reasonable trier of fact could have found defendant guilty beyond a reasonable doubt, the appellate court 'must view the evidence in a light most favorable to respondent and presume in support of the judgment the existence of every fact the trier could reasonably deduce from the evidence.'" [Citation.] The same standard also applies in cases in which the prosecution relies primarily on circumstantial evidence. [Citation.]' [Citation.] [] We therefore review the record in the light most favorable to the prosecution to determine whether the challenged convictions are supported by substantial evidence, meaning 'evidence which is reasonable, credible, and of solid value.' [Citation.] In contrast, 'mere speculation cannot support a conviction. [Citations.]' [Citation.] 'In deciding the sufficiency of the evidence, a reviewing court resolves neither credibility issues nor evidentiary conflicts. [Citation.] Resolution of conflicts and inconsistencies in the testimony is the exclusive province of the trier of fact. [Citation.]'" (People v. Mejia (2007) 155 Cal.App.4th 86, 93.)