What is the government's burden of proof in the context of evidence in the defence of an insanity defense?

The government may satisfy its burden of proof by establishing by clear and convincing evidence that the witness' claimed inability to remember is not credible. Apparently, the government introduced no affirmative evidence that Battaglia recently had told anyone about the scheme, or that his medications do not, in fact, affect long-term memory. Cf. United States v. Cooper, 465 F.2d 451 (9th Cir. 1972) (by analogy, the government has the burden of persuasion with regard to an insanity defense and must introduce affirmative evidence attacking the defendant's case).