Does a defendant have a constitutional duty to identify and identify a potential witness in advance of a trial?

The case is not a capital case, and therefore does not come within the provision of 18 U.S.C. 3432, which requires the government to furnish a defendant a list of witnesses. If the government had no duty to identify its witnesses in advance of this noncapital trial, it would seem A fortiori that it had no constitutional duty to deliver a government witness informally to the defendant for interviews in the absence of a subpoena or court order for the taking of a deposition under proper safeguards. In United States v. Thompson, 493 F.2d 305, at 309 (9th Cir. 1974), we pointed out that "the seclusion" of a possible government witness did not require reversal.