Is a witness who gives evidence at a joint trial considered a witness against a defendant if the jury is instructed to consider that testimony only against a codefendant?

"Ordinarily, a witness whose testimony is introduced at a joint trial is not considered to be a witness 'against' a defendant if the jury is instructed to consider that testimony only against a codefendant. This accords with the almost invariable assumption of the law that jurors follow their instructions [citation], which we have applied in many varying contexts." (Richardson v. Marsh (1987) 481 U.S. 200, 206 (Richardson).) As the court explained, "In Bruton [v. United States (1968) 391 U.S. 123], however, we recognized a narrow exception to this principle: We held that a defendant is deprived of his Sixth Amendment right of confrontation when the facially incriminating confession of a nontestifying codefendant is introduced at their joint trial, even if the jury in instructed to consider the confession only against the codefendant. We said: [] '[T]here are some contexts in which the risk that the jury will, or cannot, follow instructions is so great, and the consequences of failure so vital to the defendant, that the practical and human limitations of the jury system cannot be ignored.'" (Id. at p. 207.)

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