In a song from “The Music Man,” the lyric asks, “Where is the good in goodbye?” The same might well be said, in reverse, about harmless error.

The harm in harmless error is everywhere. No more pernicious doctrine has infected the legal system in the past century than harmless error. Yet, while routinely cited, it has received scant, and at times wholly inconsistent, attention by courts at every level. Along with its equally obtuse sibling “plain error,” it is a concept long overdue for serious re-evaluation.