What is the government's burden of proving the falsity of a witness's responses?

If the government seeks to have a witness held in civil contempt for the false assertion of an inability to remember, it has the burden of proving the falsity of the witness's responses. To carry this burden, the government must "establish[] by clear and convincing evidence that the witness' claimed inability to remember is not credible." Matter of Battaglia, supra, 653 F.2d at 423; cf. Stringfellow v. Haines, 309 F.2d 910, 912 (2d Cir.1962). Such evidence may include extrinsic proof, such as tape recordings, documents, or photographs; or it may be found in the witness's demeanor and his answers, if the pattern and substance of those answers convinces the court that the answers are inherently incredible.