Let me quote from that portion of his testimony, which appears on pages 512 and 513, which makes it clear that he wasn't ever claiming that he spotted that verb tense at the time in the Jones deposition, and his silence or his answer was based on spotting the verb tense then.

CNN

Now, the president's answer to Mr. Bennett's question and the statements that follow it amount to an annoying argument over the interpretation of what Mr. Bennett said, focused on the tense of the verb.

CNN

Dots over a single letter can change the tense or person of a verb, notes Keith Small, an American participant in the SOAS event.

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