[1] In his charge to the jury, the trial judge required her to prove duress by a preponderance of the evidence.

As to the second question, that of what standard would be appropriate, Justice Stevens wrote that Congress's lack of direction made the decision difficult.

The general practice at the time the statute was written (1968) was to use the common law rule giving the defendant the burden of proof by a preponderance of the evidence.

"Absent some contrary indication in the statute, we can assume that Congress would not want to foreclose the courts from consulting these newer sources and considering innovative arguments in resolving issues not confronted in the statute and not within the likely purview of Congress when it enacted the criminal prohibition applicable in the particular case."

Justice Alito agreed with Stevens, but would have held that the common law rule applied to all federal crimes absent some indication otherwise.