How can we find out whether a person talking over phone is lying or not?

Sometimes you can, but usually you cannot. If you know the person well you increase your chances of knowing whether or not they are lying to you over the phone. If you don't know them that well, then you are probably not as familiar with the speech patterns.

How can You find out whether the Person sitting in FRONT of You- is lying or not? Unless You have REALLY good "instincts", you probably can't. ... I take things I hear- with a "grain of Salt & a cube of Sugar..." That means I need to see some solid EVIDENCE of what they're saying- before I make any Judgement OR decision on it. Otherwise, what they SAY, is all the conjecture I can afford to Ignore... :)

IC is close to accurate. There are real time vocal stress analyzers which can indicate that someone is lying. Of course picking up on clues helps too, e.g."No honey, I'm at home" and hearing a bar in the background.

You give them the benefit of the doubt. Keep talking to them and keep your eye open and ears. Evenventually,you will find out the truth. They may not be lying.

You subtly bait them into answering questions that lead to them saying something that contradicts what they said earlier. It's an artform, and most people suck at it.

you do all the talking he does the listening and replies to simple line such as "ok" or "ah...ok" then call it quits. but if he is a proffesional liar you can never tell...

tape them and feed the tape to a lie detector.

because there tone of there voice changes