Listen and search for the direct denial of an accusation. 

A guilty person will try to qualify the situation by  saying words like “not really” or “not for the most part.” 

A deceptive person will get angry at the question. They may attempt to redirect the situation by accusing the questioner of discrimination or bias or by attacking a third party.

Where a response of yes or no would convey the answer, the responder launches into a convincing explanation instead of answering the question. They may add disqualifiers such as “I won’t lie to you” or “honestly” in an attempt to convince.

The person will enter a phase of fight or flight. The strain of deception will typically cause the skin to flush or to turn cold and itch. The person will scratch their ears or nose. They will answer too quickly.  They might fidget or suddenly tap nervously.

Assuming folded arms are a sign of lying behavior is speculation. 

Instead, consider whether the behavior is a result of your question, or possibly just nervousness.