Even the most experienced person who is trained to mask their expressions may still betray themselves with their bodies.
There are nonverbal cues from the subconscious, which we are not able to conscious control.
And there are other signs we give by accident because we don't realize that we are telling more than we intend to.
That is why you want to watch for signs of deception.

Cues for deception can be movements such as rubbing the side the nose, covering of the mouth with the hands, jerking the head quickly to one side or leaning away from you.
These cues are even more significant, if they occur while someone is saying something that isn't congruent with the sign.
Bear in mind; these behaviors may simply result from nervous tics, but they can also expose a liar. To accurately read body language you need to watch the signs in clusters and consider them in relation to the context.

Most people want to subconsciously apologize for a lie.
Because they feel guilty for lying many signs can be detected in their nonverbal behavior.

Generally, if someone is lying they avoid eye contact, at least during a certain part of the conversation.
Naturally, we make eye contact for at least half of a conversation.
Anything less than this could be suspicious.
But be careful; some people are so shy that they avoid eye contact with you and there are others who have learned to look you straight in your eyes whilst lying in order to convince you that they being honest.

Cues are if a person taps their foot a lot, fidgets with their hands, raises their shoulders, turns away from you or brings their hand to their face (to touch their chin or nose, etc.).
If someone comes across as being nervous or uncomfortable it could mean they're telling a lie.
Also watch out for blushing or becoming pale and increased blinking.

Some people attempt to hide a lie with a forced smile.
But a false smile looks different from a natural one.
The forehead muscles are active, the cheeks and the jaw move and the nose may wrinkle.
But most importantly a natural smile shows wrinkles beside the eyes.

A change in the pitch of someone's voice; change of tone or a lot of stammering, throat clearing and word repetitions could indicate a lie.

Rather than relying on a specific behavior, catching a liar in the act is best done by watching their normal behaviors.
When those behaviors suddenly change, that's when a lie has likely been told.

A guilty person will often try to change the subject using humor or sarcasm.
They try to change the subject.
And when the subject is changed the person appears less stressed.

If someone is lying and you change the subject, chances are high that they'll go right along with it.
A person telling the truth, however, may be confused by the sudden change in topics and will want to return to the previous subject.

If a person gives an honest answer, there isn't a lot of thinking involved. But liars have to come up with a legitimate response.
There is a good chance to find inconsistencies in their stories.
When a liar says something, it is usually on the spur of the moment.
Hence, they tend to forget what they previously said, leading to an inconsistent story.
The longer they speak about it the more the have to remember to avoid errors.
That takes time and a lot of energy!

A strategy to erase doubts is by using absolutes such as "always", "everyone", "ever" or "never".

Sometimes when someone is lying there is a tendency to become extremely defensive, refusing to answer any questions and even accusing you of lying.
This may mean they have something to hide.

To know about that is not only to catch liars but also the body language can sometimes help you trust a speaker.
Look for expansive, welcoming gestures that seem to flow naturally from the person's behavior.
Is the other one authentic and congruent?

Beware of interpreting every single little sign you observe.
Resist drawing hastily conclusions based on someone who suddenly starts scratching the neck or touching the nose.
As just mentioned; read the body language in clusters and context.
This will help you to gain insights how a person feels.
Learn how to include the full range of expressions and movements in your observation.
The human body movement includes the eyes, head, shoulders, lips, eyebrows, neck, legs, arms, fingers, hands and gestures.
The risk of reading your opponent is that you concentrate too much on just one single clue.

You can't tell for sure whether or not someone is telling the truth or is lying.
While you should trust your instinct, if you're not sure it's best to try to get some evidence to back up your accusation.

Some kind of body language (the so called minimal cues) is so inconspicuous and may only appear for the blink of an eye lid.
It needs a lot of training and awareness to identify such minimal cues.

And there is another aspect to be taken into account; if someone believes in his "lie" the chance is high that there are only a few or no cues at all.

Reading the body language may not be 100% accurate all the time.
But by combining all the cues, you'll come up with reliable data supporting your assertions.
There are a lot of aspects to be taken into account to make an educated guess on whether someone is telling the truth or a lie.
Knowledge and training are essential to be able to accurately read body language.