Daniel Epps, Harmless Errors and Substantial Rights. 131 HARV. L. REV. 2117 (2018).
The harmless constitutional error doctrine is as baffling as it is ubiquitous. Although appellate courts rely on it to deny relief for claimed constitutional violations every day, virtually every aspect of the doctrine is subject to fundamental disagreement and confusion. Judges and commentators sharply disagree about which (and even whether) constitutional errors can be harmless, how to conduct harmless error analysis when it applies, and, most fundamentally, what harmless constitutional error even is — what source of law generates it and enables the Supreme Court to require its use by state courts. This Article offers a new theory of harmless constitutional error, one that promises to solve many of the doctrine’s longstanding mysteries.