How to tell someone's lying to you by watching their face

Just about everyone you know tells low-stakes lies, but some people even go so far as to lie about important matters that could forever change their relationships, end their employment, or even send them to jail.

Detecting high-stakes liars 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 facial expressions to detect lies can be beneficial even if you're not conducting criminal investigations, he says.

"There are a number of facial expressions and associated reactions that could indicate someone is lying to you," he says. "Some are caused by nervousness, some by chemical reactions, and others by physical reactions."

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," he 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 are some of the facial expressions Bouton suggests looking out for: