The legal doctrine of harmless error is found in the Federal Rules of Criminal Procedure, extensive case law, and state statutes. It comes into use when a litigant appeals the decision of a judge or jury, arguing that an error of law was made at trial that resulted in an incorrect decision or verdict. The appellate court then must decide whether the error was serious enough to strike down the decision made at trial. Review for harmless error involves a complicated test that applies to state and federal laws as well as rules of procedure. If an error is held to be serious, the appellate court is likely to set aside the decision of the trial court and may order a new trial. If it deems the error harmless, the appellate court affirms the lower court's decision. The doctrine of harmless error thus prevents an unnecessary new trial when the error alleged would not have affected the outcome at trial.
Harmless error jurisprudence grew out of a late-nineteenth-century development in english law. Before 1873, English courts automatically reversed decisions in cases where an error was committed at trial. In 1873, Parliament put an end to this practice in civil cases by permitting reversals only in cases of substantial error. As the author Raymond A. Kimble has noted, U.S. law slowly adopted the idea in order to limit the number of retrials in U.S. courts.
In 1919, Congress first applied the harmless error doctrine to federal appellate courts, ordering them "to give judgment after an examination of the record without regard to errors or defects which do not affect the substantial rights of the parties" (28 U.S.C.A. § 2811 ). By the midtwentieth century, harmless error jurisprudence was growing. The U.S. Supreme Court first moved toward establishing harmless error analysis in the 1946 case of Kotteakos v. United States, 328 U.S. 750, 66 S. Ct. 1239, 90 L. Ed. 1557, but left doubt about its applicability to constitutional errors. It began to remove this doubt in 1967 in the landmark case of Chapman v. California, 386 U.S. 18, 87 S. Ct. 824, 17 L. Ed. 2d 705. The Court in Chapman ruled that defendants were not necessarily entitled to a new trial simply because constitutional violations had occurred at trial. It directed appellate courts to dismiss arguments about certain constitutional errors when these "are so unimportant and insignificant that they may, consistent with the Federal Constitution, be deemed harmless, not requiring automatic reversal of a conviction."However, the Supreme Court put an important condition on this analysis: the appellate court had to be certain beyond a reasonable doubt that the error did not affect the outcome of the case.
Even decades after Chapman, determining whether a constitutional error is harmless remains a complicated task. This is because harmless error has no single, uniform definition. Courts must resort to one of two distinct tests—and sometimes a third that combines both of them. The first test asks whether the error influenced the verdict. If the error did not have even a minimal effect on the verdict, it is harmless. The second test considers the evidence of guilt found in the trial record. If the evidence is overwhelming and untainted, the defendant's guilt is considered to be the most important factor, and the error is harmless. The third test is a balancing test in which the court weighs the error's effect on the verdict against the untainted evidence. The court may emphasize either element in this test, and the outcome of the test will reflect which is considered stronger.
The harmless error doctrine has continued to evolve since the late 1960s. For many years, there was still uncertainty about which constitutional errors at trial could be subject to harmless error analysis, but the Supreme Court has clarified this by allowing most constitutional errors to be reviewed under the doctrine. Some of its decisions have proved controversial. In the 1991 case of Arizona v. Fulminante, 499 U.S. 279, 111 S. Ct. 1246, 113 L. Ed. 2d 302, for example, it included coerced confessions under the scope of harmless error review. This decision curtailed the ability of criminal defendants to overturn their conviction by arguing that the police used physical or emotional force to win a confession. As a result, appellate courts are free to determine if the jury had enough evidence besides the challenged confession to convict a defendant. As part of a general trend, this expansion of the scope of harmless error analysis has raised complaints about the proper role of appellate review.
Cooper, Jeffrey O. 2002. "Searching for Harmlessness: Method and Madness in the Supreme Court's Harmless Constitutional Error Doctrine." University of Kansas Law Review 50 (January): 309–45.
Kimble, Raymond A. 1995. "Casenote: Harmless Error." Seton Hall Constitutional Law Journal (spring).
Landes, William M., and Richard A. Posner. 2001."Harmless Error." Journal of Legal Studies 30 (January): 161–92.
Mitchell, Gregory. 1994. "Against 'Overwhelming' Appellate Activism: Constraining Harmless Error Review." California Law Review (October).