If you're having a conversation with someone you suspect is being less than truthful, study more than the person's assertions, denials and guarantees to measure his honesty. Scrutinize his involuntary movements and mannerisms for nonverbal communication cues that can indicate apprehension or guilt because he knows he's lying to you.
Forbes magazine notes that a liar may be unable to control physical cues that indicate nervousness, such as sweating, squirming in his seat or shuffling from foot to foot as he speaks. A person telling you a lie, particularly one who isn't accustomed to being untruthful, may also touch his face or place his fingertips on his lips as if he's subconsciously trying to keep the untruth from leaving his lips.
A dishonest person's facial expression may give her away, the Career Builder website observes. Instead of reacting naturally as she makes a statement, a liar may tell a "sad" lie with a straight face, but then lower her eyes and frown when she remembers that she's supposed to be upset, for example. A liar pretending to be happy may wear an insincere smile that vanishes from her face immediately after she tells the lie instead of lingering naturally. The Health Guidance website states that a liar may purse her lips during the conversation, while her brow furrows as she works to remember the details of her lies.
Take a tip from the Health Guidance website and study that other party's body language if you suspect he's lying. The website notes that a liar may raise his shoulders slightly and press his elbows into his sides to subconsciously make his body "shrink" to avoid scrutiny. A dishonest person may also keep his arms folded or cross his legs or ankles if he's sitting to construct a "barrier" between you.
Study the other party's eye contact if you're trying to spot dishonesty. The Working Knowledge website of the Harvard Business School states that a liar may avoid maintaining eye contact throughout the conversation. Use eye contact in combination with facial expressions or body language to assemble the complete picture since the site notes that a pathological liar may be aware that you're studying her eye contact, so she may purposefully hold your gaze to appear honest.
When trying to determine if a person is lying in a text message or email, evaluate his words to look for signs of dishonesty. The hospital notes that a liar may not use "I" or "my" in the text in a subconscious attempt to disconnect himself from the lie or avoid accountability. He may also omit words that convey emotion or understanding, such as "angry" or "sad," since he may feel detached from the lies he's telling in the text.