In a sexual assault case, is third party evidence admissible?

In determining whether to give requested instructions on third party culpability, courts often rely, as did the trial court here, on the language in People v. Hall (1986) 41 Cal.3d 826, 833: "To be admissible, the third-party evidence need not show 'substantial proof of a probability' that the third person committed the act; it need only be capable of raising a reasonable doubt of defendant's guilt. At the same time, we do not require that any evidence, however remote, must be admitted to show a third party's possible culpability. . . . [E]vidence of mere motive or opportunity to commit the crime in another person, without more, will not suffice to raise a reasonable doubt about a defendant's guilt: there must be direct or circumstantial evidence linking the third person to the actual perpetration of the crime."