This new law review article by Daniel Epps examine the subject in depth. Consider this excerpt from the abstract:
Judges and commentators sharply disagree about which (and even whether) constitutional errors can be harmless, how to conduct harmless-error when it analysis 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.
No such thing as a harmless Constitutional error. The Constitution was written for a reason and one was for the protection of the citizen from government abuse. The courts have already destroyed the ex post facto clause. Why are we allowing them to continue to destroy what protections we have?
Please explain the comment re the courts destroying the ex post facto clause. What courts have allowed an ex post facto application of a prohibitory statute?