When one testifies under oath and one knows something that one would rather not say -- or that one's boss would rather not have you say -- you pay extremely close attention to the questions. You answer the question, and nothing but the question. If the question is extremely troublesome, you answer it as narrowly as possible, and you hope that your questioner will not follow up on any slip you might make.

If you don't care about what the boss thinks, or you want to make a clean breast of things, you just answer. You answer completely, effusively even, and include details that would not be included in the testimony of someone whose agenda was to restrict access to information.

It's quite possible for one person to be in both positions at different times on the same subject.

In the meantime, it would be wise not to remark on the contents of testimony that has not been released. As far as we know, "innocent until proven guilty" is still the law in the United States, even as it applies to perjury accusations against Mr. Clarke. "He must be lying because this can't be true" will not wash.