How to tell someone's lying to you just by watching their body language

Everyone gets lied to now and then, but when the stakes are high, knowing the difference between a truth and a lie can save the day.

Detecting high-stakes lies is often the work of the FBI, and they frequently look to facial expressions, body language, and verbal indicators as signals, or "tells," that someone is lying.

Mark Bouton, an FBI agent for 30 years and author of "How to Spot Lies Like the FBI," tells Business Insider that he used certain tells to help identify Timothy McVeigh as a suspect in the Oklahoma City bombing.

But being able to read body language to detect lies can be beneficial even if you're not conducting criminal investigations, he says.

The physical and emotional responses of the human body operate within all of us, Bouton says, and recognizing certain responses can help infer someone's lying.

To start, he says it's important to understand how the person in question normally acts.

"It's best to observe someone for a while as you make small talk or ask innocuous questions, in order to see what his usual reactions are, including tics he may have," Bouton says. "Then if he exhibits several lying indicators when you ask more pointed or suggestive questions, and these are not ones he previously performed, you can be confident that he's likely lying."

Here's some of the body language Bouton looks out for: