Rule 607 of the Federal Rules of Evidence provides: 'The credibility of a witness may be attacked by any party, including the party calling him.'
It would be an abuse of the rule, in a criminal case, for the prosecution to call a witness that it knew would not give it useful evidence, just so it could introduce hearsay evidence against the defendant in the hope that the jury would miss the subtle distinction between impeachment and substantive evidence -- or, if it didn't miss it, would ignore it. The purpose would not be to impeach the witness but to put in hearsay as substantive evidence against the defendant, which Rule 607 does not contemplate or authorize.
'Impeachment by prior inconsistent statement may not be permitted where employed as a mere subterfuge to get before the jury evidence not otherwise admissible.' United States v. Morlang, 531 F.2d 183, 190 (4th Cir. 1975). Although Morlang was decided before the Federal Rules of Evidence became effective, the limitation that we have quoted on the prosecutor's rights under Rule 607 has been accepted in all circuits that have considered the issue. See, e.g., United States ...