What is the meaning of evidence the exclusion of which would violate the constitutional rights of the defendant in United States Federal Rules of Evidence 412

In United States Federal Rules of Evidence 412, evidence the exclusion of which would violate the constitutional rights of the defendant refers to evidence that is related to the sexual behavior or predisposition of the alleged victim in a criminal sexual assault case. This type of evidence is usually considered irrelevant and inadmissible in court because it can be prejudicial to the victim and distract from the facts of the case. However, if the exclusion of such evidence would violate the defendant's constitutional rights, such as the right to confront witnesses or the right to present a defense, it may be admissible