William J. Brennan, Jr.

“ Bruton and Roberts, therefore, compel the conclusion that the Federal Constitution forbids the States to assume that juries can follow instructions that tell them to wipe their minds of highly damaging, incriminating admissions of one defendant that simultaneously incriminate another defendant whose guilt or innocence the jury is told to decide. In the present case, California itself has made the judgment that, although Runnels did take the stand, his extrajudicial statements could not be considered by the jury as evidence against respondent. ”

“ Under the law of California at the time of respondent's trial, admissions to a police officer by a criminal defendant after his arrest could not be used as substantive evidence against other defendants, whether or not the declarant testified at trial. [1] The question with which we are faced is not, therefore, whether the Sixth Amendment would forbid California from using Runnels' statement as substantive evidence against respondent O'Neil if it chose to do so. ”

“ For the inevitable result of this procedure is that, in fact, different rules of evidence will be applied to different defendants depending solely upon the fortuity of whether they are jointly or separately tried. ”