Nobles (D) was tried and convicted on charges arising from an armed robbery of a bank. The strongest evidence was the identification testimony of two witnesses, a bank teller and a salesman who was in the bank during the robbery. D offered an alibi but his strongest defense centered around attempts to discredit these eyewitnesses. D's efforts to impeach them gave rise to the events that led to this decision. An investigator for the defense interviewed both witnesses and preserved the essence of those conversations in a written report. When the witnesses testified, D's counsel relied on the report in conducting their cross-examination. Counsel asked the bank teller whether he recalled having told the investigator that he had seen only the back of the man he identified as D. The witness replied that he did not remember making such a statement. He was allowed, despite D's initial objection, to refresh his recollection by referring to a portion of the investigator's report. The prosecutor also was allowed to see the relevant portion of the report. The witness thereafter testified that although the report indicated that he told the investigator, he had seen only respondent's back, he had seen more than that and continued to insist that D was the bank robber. D's counsel twice inquired whether the second witness told the investigator that 'all blacks looked alike' to him, and in each instance, the witness denied having made such a statement. The prosecution again sought inspection of the relevant portion of the investigator's report, and D's counsel again objected. The court declined to order disclosure at that time but ruled that it would be required if the investigator testified as to the witnesses' alleged statements from the witness stand. The court further advised that it would examine the investigator's report in camera and would excise all reference to matters not relevant to the precise statements at issue. D called the investigator as a defense witness. The court reiterated that a copy of the report, inspected and edited in camera, would have to be submitted to Government counsel at the completion of the investigator's impeachment testimony. D's counsel stated that he did not intend to produce the report. The court ruled that the investigator would not be allowed to testify about his interviews with the witnesses. The Court of Appeals for the Ninth Circuit considered it reversible error; the Fifth Amendment prohibited the disclosure condition imposed in this case. The court further held that Fed. Rule Crim. Proc. 16, while framed exclusively in terms of pretrial discovery, precluded prosecutorial discovery at trial as well. The Supreme Court granted certiorari.