Orin Kerr has an interesting summary of the case Dixon v. United States. You will forgive me if I don’t try to summarize the case since Kerr does a much better job than I could imagine of doing.
While, based on Orin’s summary, the case probably was correctly decided, I’m disappointed that the default burden of proof does not lie with the government. It seems to me that an individual’s rights are protected to the greatest extent by limiting government power.
However, Alito’s concurrence makes a lot of sense to me. Common law dating from before the Constitution states that if a defendant is going to use duress as a defense they must provide the burden of proof. Since Congress has never addressed duress as a defense courts should assume that common law applies.
I also agree with Alito that attempting to determine where the burden of proof lies by trying to discern what common practice was at the time that a statute was passed by Congress is overly burdensome.