I read recently (sorry, can't remember where as I'm half-senile) that it's far easier to detect lying over the phone than facially. Some experiments with students showed they succeeded far more often in detecting a lie from a volunteer on the phone than from one sat in front of them. Apparently, a voice conveys much more to our 'intuition' than facial expressions do. I also read (maybe the same article) that so-called standard 'giveaways' are never reliable. A liar can look one directly in the eye and may not be 'shifty' at all. I've seen this in my pupils in class - they used to gaze appealingly into my eyes as they lied through their teeth, the little horrors. Also, a person telling the truth may be nonetheless nervous and unable to stop twitching or stammering etc. Those Border Control programmes are fascinating, as the Customs people at ports or airports have such enormous experience that they can spot a smuggler or an illegal immigrant a mile away. I've also spoken to Police who told me they can cruise the streets in a Police car and spot a criminal on the pavement easily just by instinct and experience.