I trust and respect you enough to take you on your word that a specific individual trained in the art of the varied techniques of lie detection displayed above chance results. If it were her saying that Gordon was lying then her track record is relavent. However her track record is vindication of her personal mastery of a variety of techniques, not a specific indicator in isolation. That alone coming from someone who as far as I know doesn't have the same level of experience or proven track record is not good enough on it's own to count Gordons statement as a lie.
That said its still possible that he's lying and given the implausibility of his statement I wouldn't be in the slightest bit suprised if he was.