1. Does the Constitution permit the exclusion of a defendant's presentation of substantial evidence of third-party culpability simply because the court believes the prosecution has presented evidence of the defendant's guilt?

2. May a court condition the presentation of a third-party culpability defense upon the defendant demonstrating that there is "direct or circumstantial evidence linking the third person to the actual perpetration of the crime"? And, if so, may a court apply that standard to require a defendant to disprove any circumstances that may exculpate the third party before being permitted to present the defense to the jury?

Does the Constitution permit the exclusion of a defendant's presentation of substantial evidence of third-party culpability simply because the court believes the prosecution has presented evidence of the defendant's guilt?