Anxiety: 

Every liar feel anxious. Spot the state of anxiety by seeing if the person bites nail, change the sitting position frequently, sweating or tapping hands on his lap.Try to talk more and more about the subject to make the person more anxious and detect the lie. Anxious person find difficulty in speaking the right words and doing the right actions. Body of an anxious person also become rigid in some cases because he want to prevent others on paying attention to him.