Good interviewers are analysts of human behaviour and can tell when a person might be deceiving them, says "the lie guy", Steve Van Aperen.
It's actually very difficult for the average person to lie, says Van Aperen, who has trained with the FBI and other investigative authorities, and conducted both employment and criminal interviews.
Lying requires a lot of effort, because "when delivering a deception, we're trying to think of what we want to say and make it sound believable or credible", whereas telling the truth is much easier because a person can rely on their memory.