William J. Brennan, Jr.

“ By its nature, the issue of substantiality of evidence admits of only the most limited kind of appellate review. Thus, the Court's rule will often effectively leave the vindication of constitutional rights solely in the hands of trial judges. ”

“ Certan ly, the State has not carried its burden of demonstrating beyond a reasonable doubt that these two confessions did not contribute to Harrington's conviction.
There should be no need to remind this Court that the appellate role in applying standards of sufficiency or substantiality of evidence is extremely limited. To apply such standards as threshold requirements to the raising of constitutional challenges to criminal convictions is to shield from attack errors of a most fundamental nature and thus to deprive many defendants of basic constitutional rights. ”

“ The Court holds that constitutional error in the trial of a criminal offense may be held harmless if there is 'overwhelming' untainted evidence to support the conviction. This approach, however, was expressly rejected in Chapman, supra, at 23, 87 S.Ct., at 827, and with good reason. For, where the inquiry concerns the extent of accumulation of untainted evidence rather than the impact of tainted evidence on the jury's decision, convictions resulting from constitutional error may be insulated from attack. ”