William J. Brennan, Jr.

“ The statute, while delimiting the statements which are to be turned over to the defense, obviously comprehends that statements which are producible under it must be given to the defense regardless of a judge's opinion as to how useful they might be on cross-examination, for only the defense can fully appreciate their possible utiity for impeachment. ”

“ In short, only a very strict standard is appropriate for applying the harmless error doctrine in these cases. Under such a standard, I cannot conclude that defense counsel could not have put Miss Vossler's letter to effective use in impeaching her. Although she stated on cross-examination that she had refreshed her memory before testifying by reference to a statement she had made previously, this oral testimony was obviously not as useful for impeachment purposes as her written admission shortly before trial that her memory of the events in question was failing. ”

“ It is rather, even so, whether the error itself had substantial influence. If so, or if one is left in grave doubt, the conviction cannot stand.' Kotteakos v. United States, 328 U.S. 750, 765, 66 S.Ct. ”