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

"As a general matter, the ordinary rules of evidence do not impermissibly infringe on the accused's right to present a defense. Courts retain, moreover, a traditional and intrinsic power to exercise discretion to control the admission of evidence in the interests of orderly procedure and the avoidance of prejudice. [Citations.] . . . [T]his principle applies perforce to evidence of third-party culpability . . . ." (People v. Hall (1986) 41

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