United States v. Smith, No. 14-60926 (5th Cir. Feb. 10, 2016).
Police found that someone had downloaded 26 child-pornography videos onto defendant James Smith’s laptop. His trial turned largely on alibi witnesses. If the jury believed Smith’s parents and girlfriend that he was at his parents’ home at when some of the videos were downloaded, then they’d be inclined to believe Smith’s central claim: that it wasn’t he, it was his roommate, who downloaded the videos. In closing arguments, the prosecutor argued that while the alibi witnesses might have an incentive to dissemble, the government had no incentive to prosecute an innocent man: “What incentive is there for us to come in and try a person if he’s not the person who did the offense?” The jury ended up convicting Smith.
The prosecutor’s rhetorical question in his closing argument was “vouching”: it was offering the integrity of the government as a reason to disbelieve the alibi witnesses. More specifically, it was an attempt to get around the presumption of innocence. It was the government’s job to say to the jury, “Here are reasons to disbelieve the defendant’s witnesses,” rather than to say, barely implicitly, “You should demand some reason to disbelieve me.”
The centrality of the alibi witnesses makes the government’s vouching particularly prejudicial. Even reviewing the vouching for plain error, the Fifth Circuit reverses the conviction and remands for a new trial.