What is the test for giving a defendant an opportunity to present a complete defense in a criminal case?

"[T]he Constitution guarantees criminal defendants 'a meaningful opportunity to present a complete defense.' " (Crane v. Kentucky (1986) 476 U.S. 683, 690, quoting

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California v. Trombetta (1984) 467 U.S. 479, 485.) With certain exceptions, however, "evidence of a person's character or a trait of his or her character (whether in the form of an opinion, evidence of reputation, or evidence of specific instances of his or her conduct) is inadmissible when offered to prove his or her conduct on a specified occasion." (Evid. Code, 1101, subd. (a).)