An “Unfortunate Bit of Legal Jargon”: Prosecutorial Vouching Applied to Cooperating Witnesses

By:  Rajan S. Trehan


Vouching, which developed out of the Supreme Court’s desire to protect the jury’s right to evaluate credibility, traditionally forbids prosecutorial statements designed to enhance or attest to the credibility of a government witness. This Note examines a flavor of vouching unique to cases involving cooperating witnesses. Prior to testifying, cooperating witnesses sign an agreement setting out the terms of their deal with the government, including a requirement of truthful testimony. Three circuits, the Second, Ninth, and Eleventh, utilize vouching doctrine to restrict references during trial to such truthful-testimony provisions. The Second and Eleventh Circuits only permit references when the cooperator’s credibility has been attacked by the defense, which is known as the “invited response” doctrine. The Ninth Circuit has displayed a willingness to completely foreclose references to such a provision. On the other side of the split, a majority of circuits allow a cooperator’s plea agreement to be put before the jury in its entirety when the prosecution wishes. This Note concludes that this split should be resolved in favor of the majority approach, which will provide much needed clarity to lawyers on both sides of the criminal bar and return vouching doctrine to its principles.



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