Lie detection is a tricky yet viable skill that can be used to ferret out deception in those you are speaking to. The basics of face-to-face lie detection involve establishing a baseline with innocuous questions, then testing that baseline to spot signs of evasion or deceit. But what happens when you're speaking to someone on the phone? You don't have the tics and mannerisms of the other person's face to work with. Fortunately, there are still telltale verbal cues that allow you to spot a liar even when the voice is all you have to go on.
Establish a baseline by chatting casually with the person. Pay attention to the pattern of his speech, the flow of his words and the way he pronounces his sentences. Ask him about the weather, about local sports teams or subjects of similar interest. The aim is not to be interrogative but to put the subject at ease.
Shift to the core of the issue and listen for shifts in the pattern of speech. The most obvious is a long pause before answering: the person is probably looking for the right words, which suggests some manner of deceit. In addition, listen to the flow of the person's words for changes in tempo--speaking more slowly or quickly, or using more guarded terms of speech. In the most general terms, a relaxed speaker is often telling the truth (or at least has practiced his lie enough to be comfortable with it), while an awkward, nervous or halting speaker is more likely to be lying.
Look for attempts to change the subject. A liar will often avoid speaking about the topic directly, and instead will attempt to shift the conversation somewhere else. She may also use evasive or non-responsive answers, addressing your questions without actually providing any details. (The old "my cell phone is breaking up" routine is pretty obvious, but that doesn't mean people still don't use it.)
Expect hostility. Arguments and accusations are often used to obscure the issue, getting the liar off the hook by couching the confrontation in "he said, she said" terms. Don't take the bait. Remain calm and on-topic, focusing the conversation on the pertinent issue. If he continues to bluster, there's a good chance he's got something to hide.
Check for other methods of creating confusion. A liar may repeat questions given to her, rephrase previous answers and otherwise seek to obfuscate the topic of conversation. It provides her with another means of escaping the painful questions. Stay clear and direct if she tries this; it gives her much less room to hide.
Lie detection is a matter of instinct as much as certainty, and people who lie may not be doing so for actively malicious reasons. Use your best judgment when trying to ascertain if someone on the phone is lying, but refrain from direct accusations unless you feel you have sufficient evidence.