Two years ago the Fifth Circuit Court of Appeals said that a prosecutor’s role “is not that it shall win a case, but that justice shall be done.”


In their too often misguided zeal to secure convictions, prosecutors will knowingly engage in misconduct to “win a case.”  With increasing frequency, federal prosecutors are engaging in this form of misconduct by bolstering or vouching for government witnesses.


In a 2002 Criminal Justice Magazine article titled “Permissible, Impermissible Corroboration of Witnesses,” George Washington University School of Law Professor Stephen A. Saltzburg pointed out the slight difference between the two forms of misconduct.


Vouching vs. Bolstering


Professor Saltzburg said that “’improper vouching occurs when a prosecutor supports the credibility of a witness by indicating a personal belief in the witness’s credibility thereby placing the prestige of the office of the United States Attorney behind that witness…’” With respect to bolstering, Saltzburg said it “occurs when the prosecutor implies that the witness’s is corroborated by evidence known to the government but not known to the jury.”


In its 2016 decision, United States v. Smith, the Fifth Circuit said that both of these trial tactics amount to misconduct when they cross the line between permissible and impermissible witness corroboration. These forms of prosecutorial misconduct have been occurring with greater frequency in federal drug conspiracy trials, particularly in the Southern District of Texas. The tactics are accomplished when prosecutors use a “truthfulness” provision of a co-conspirator plea agreement to either vouch for or to bolster the co-conspirator’s testimony against the defendant.


Guilty Plea of Co-Defendant Cannot be Substantive Evidence


Federal case law has been clear for more than three decades that a co-defendant’s “guilty plea may not be used as substantive evidence of a defendant’s guilt.” This rule is premised on the widespread judicial recognition that juries are likely to believe that if one defendant pleads guilty, then any co-defendant must also be guilty.


As far back as 1979, the Fifth Circuit has explicitly held that “a defendant is entitled to have the question of his guilt determined upon the evidence against him, not on whether a codefendant or government witness has been convicted of the same thing.”


Conspiracy Drug Cases and Cooperation


Most federal drug cases involving a charged conspiracy entails one or more of the co-conspirators securing a plea agreement from the government. These agreements generally exchange testimony against the defendant for a benefit, usually a recommendation by the government for a reduced sentence. These agreements, more often than not, have a “truthfulness” component requiring the co-conspirator to tell “the truth, the whole truth and nothing but the truth” during the pretrial investigative process and particularly at trial when the co-conspirator testifies against the defendant.


Federal prosecutors are aware of the well-established case law that a co-conspirator’s guilty plea is admissible only for the limited purpose of aiding the jury’s assessment of the co-conspirator’s credibility, and most definitely may not be used as evidence of a defendant’s guilt. This longstanding rule applies even to those agreements with a truthfulness component.


Truthfulness Provision of Plea Agreement


This case law instruction to federal prosecutors, as well as to federal trial judges, does not deter some prosecutors from using the truthfulness provision to improperly bolster or vouch for a co-conspirator’s credibility. This kind of prosecutorial misconduct effectively places a stamp of personal approval on the co-conspirator’s testimony by the U.S. Attorney’s Office. The prosecuting attorney is essentially telling the jury: “we guarantee that the co-conspirator is telling ‘the truth, the whole truth, and nothing but the truth’ because we made it part of our plea agreement with him and there is no agreement without the truth.”


Rules of Professional Conduct


The Rule 3.4(e) of the Model Rules of Professional Conduct (2016) prohibits a lawyer from stating “a personal opinion as to the justness of a cause, the credibility of a witness, the culpability of a civil litigant or the guilt of an accused.”


As the D.C. Circuit Court of Appeals stated this ethical rule five decades ago: “ … it [is] for the jury, and not the prosecutor, to say which opinion on guilt or innocence.”


Criminal defense attorneys practicing in the Southern District of Texas need to be mindful of this trend by federal prosecutors to use improper bolstering and vouching in drug conspiracy cases and be prepared to make the proper objection to preserve the matter for appeal.