What is the test for presenting evidence of third party culpability in a criminal case?

"A criminal defendant has a right to present evidence of third party culpability if it is capable of raising a reasonable doubt about his own guilt. The rule does `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.' [Citation.]" (People v. Sandoval, supra, 4 Cal.4th at p. 176, 14 Cal.Rptr.2d 342, 841 P.2d 862, quoting People v. Hall (1986) 41 Cal.3d 826, 833, 226 Cal.Rptr. 112, 718 P.2d 99.)