There are many cues that may help you distinguish someone who is lying from someone who is telling the truth. Some involve body language, such as how a person sits or how she moves. Others involve eye movement; some movements indicate a retrieval of memory, others indicate an accessing of creative abilities. Looking for these cues is hindered if the person is not sitting physically in front of you, however. Instead you must look for cues in the person's voice alone. There are several ways that people betray that they're lying through their voice.
Listen first to the pitch of the potential liar's voice. Is he speaking in a slightly higher pitch? When people lie, muscles in their bodies contract, including their voice muscles. This causes their voices to raise in pitch.
Listen for the speed of her words. Liars often will speak quickly to get the lie over with, and to keep you from asking follow-up questions or interrupting the flow of their rehearsed story.
Listen for the person to repeat most of the question in his answer. If he does, chances are he is lying. For instance, if you ask someone "Did you scratch my car?" and he responds "I did not scratch your car," it's more likely that he's lying than if he simply responded "No."
Check if the person uses contractions in her response. If she doesn't, it's more likely that she's lying. So, someone who answers "I did not scratch your car" is more likely to be lying than someone who says "I didn't scratch your car."
Listen for the person to make any throat clearing or coughing sounds. When a liar's muscles contract, oftentimes breathing gets strained, and he may clear his throat to counteract this.