is a tendency towards vagueness in an untruthful account of events.
A technique used by some interrogators when they believe they have been told a lie is to carry on the conversation for a while and then repeat the same question a bit later. The liar is likely to be rattled by this because it registers as a challenge and they have to rapidly recall exactly what they said previously.
Blushing may be a giveaway; most obviously it is provoked by embarrassment but it is also associated with a sense of shame or guilt and hence may suggest lying. The same applies to other signs of autonomic arousal, such as sweating, blinking, pupil dilation, increased swallowing and changes in breathing patterns. Of course, like voice tremors, these are general stress signs and there may be reasons for feeling stressed other than lying. Care should be taken not to discount these other possibilities.
Biting the lip and puckering of the mouth also suggest some kind of tension as though the individual is trying to intercept an inadvertent spilling of the truth they are trying to withhold.
The hand-shrug (waving a single hand outwards) may effectively discard what the person is saying as unreliable. However, opening the palms symmetrically is more likely to be a sign of openness (having nothing to hide).
Attempts at deception are sometimes betrayed by what is not seen rather than what is observed. For example, if a person is recounting a traumatic experience, then the absence of distress signs (e.g. a tear in the corner of the eye or a crinkling of the brow