Though it would seem to go without saying, prosecutors aren’t supposed to introduce evidence they know to be false. But government attorneys sometimes bend—and break—the rules. In that kind of situation, where the prosecution gets a conviction on testimony it knows to be false, the reviewing court is supposed to reverse the conviction on due-process grounds.
In the 1930s, Henry Napue was convicted of the murder of an off-duty policeman during a shootout in a Chicago cocktail lounge. Most of the evidence against him came from one of his fellow shooters, who testified that he didn’t receive any promises for his testimony. That was a lie; the prosecutor had promised that he would work to reduce the witness’s sentence if the witness testified. Napue found out about the offer of leniency and filed a petition, but the Illinois courts denied it.
Napue appealed to the U.S. Supreme Court, which created a three-part test to determine whether a conviction in this kind of case violates due process. The Court said that, if a defendant can prove each point, then his or her conviction is no good. The defendant must establish that:
With the requirement that false testimony be “material,” the Supreme Court meant that there must be “a reasonable likelihood that the false testimony could have affected the judgment.” The Supreme Court found that the false statement in Napue’s case could have affected the jury’s verdict, so it reversed his conviction. (Napue v. Illinois, 360 U.S. 264 (1959).)
In 2013, a federal appeals court considered the case of a man named Dow. Dow had been convicted of robbing a convenience store in California. The cashier had changed his description about the location of a scar on the suspect several times and had to view a lineup twice. During the second lineup, Dow’s lawyer was present and noticed that his client was the only one in the lineup who had a scar. So, he asked that all of the men in the lineup be made to wear a bandage under the eye where Dow had a scar. That way, the lineup would be fairer.
At trial, a police officer testified that Dow—not his lawyer—was the one who asked that everybody wear a bandage. The prosecutor knew that this wasn’t true, but he nevertheless argued to the jury that Dow asked to wear the bandage because he knew he was guilty.
Dow challenged his conviction with a habeas corpus petition. A lower court denied the petition, finding that the false testimony would not have affected the case’s outcome. But the federal appeals court reversed the conviction. Applying the Supreme Court’s rule in Napue, the appeals court found that the lower court had applied the wrong standard: The question isn’t whether the false testimony would have affected the verdict, but whether it could have. Because the trial court applied the wrong standard—one that’s tougher for defendants to meet—the appeals court reversed Dow's conviction. (Dow v. Virga, 729 F.3d 1041 (9th Cir. 2013).)
If you believe the government used false testimony or other dodgy evidence against you, seek the advice of an attorney about your options. Although U.S. Supreme Court cases on false testimony apply across the whole country, different courts may be more open than others to reversing a case on this basis. Plus, the laws of some states might be even more protective of criminal defendants than the federal Constitution as interpreted by the Supreme Court. Differences in law aside, an experienced criminal defense attorney is vital because of training and knowledge. A good lawyer will vastly improve your chances of presenting a successful argument.