Note How He Speaks
Observing a person's way of delivering his speech is somewhat tricky. You may have to know first how he normally speaks before judging his sincerity or honesty. But if you already know the speech habits of the person, then it would be less difficult to detect lying. The volume of the voice would be softer than usual, but during a defensive state of mind, he would usually raise his voice. Then there would be some speech errors, such as mispronunciation, stuttering, or stammering. The pacing of the way he talks would also be faster.
Other Signs Of Lying
Another sign of lying is when the person would tend to touch himself when he delivers his lies. Self touching gestures include rubbing the nose, scratching the forehead, and touching the nape, elbow, or other parts of the body. Self touching is a strong indication of discomfort and guilt.
Observe also the rest of the body. Note if the person is trembling, fidgeting, or shaking. But these actions are usually found during extreme nervousness. A stiff posture with the elbows pulled to the sides and tightened muscles is a posture which reflects lying as well.
The meanings and interpretations of the different acts and signals of body posture are not always true and definitive. This is one of the risks in reading other people's body language. You may be too quick to judge their honesty and even their whole personality. Thus, be careful in interpreting other's gestures and body movements.
The last thing you would want to happen is a conflict due to miscommunication and misinterpretation.