Sixty years ago, in Kotteakos v. United States, the Supreme Court ruled that a small class of so-called harmless errors committed by courts did not require correction. The Court acknowledged that some judicial errors, though recognizable as errors, did not threaten the validity of criminal convictions and therefore did not quite require reversal. Specifically, the Court held that errors that violated federal statutes should be deemed harmless unless they had a "substantial and injurious effect or influence in determining the jury's verdict." While Kotteakos represented the Supreme Court's first treatment of the concept of harmlessness, other courts had a history of preserving convictions using harmless error review. For some time before Kotteakos, state statutes had directed appellate courts throughout the country to use harmless error review, a doctrine that prevents appellate courts from disposing of convictions on technicalities, "conserve[s] judicial resources by enabling appellate courts to cleanse the judicial process of prejudicial error without becoming mired in harmless error," and allows courts to focus on "decid[ing] the factual question of the defendant's guilt or innocence."
Jeffrey S. Jacobi,
Mostly Harmless: An Analysis of Post-AEDPA Federal Habeas Corpus Review of State Harmless Error Determinations,
Mich. L. Rev.
Available at: https://repository.law.umich.edu/mlr/vol105/iss4/5