It might result hard to conceal panic. A liar could be acknowledge the feeling but lie about what brought it about. Misidentifying the cause of the emotion, the person could claim that he/she is perfectly innocent and panicked only because she fears he won’t be believed. Truthful about the felt emotion, the lie misleads about was was the cause of the emotion.
Another way is to tell the truth but with a twist, so that the victim does not believe it. Exaggerating the truth would ridicule the other part, making it difficult for him/her to pursue his/her suspicious line.
A mocking tone of voice or expression would do the trick too.