Honesty may be the best policy, but it's not a policy people follow very often. In fact, according to a Cornell University study, people lie in roughly 25 percent of their daily interactions. How can you detect dishonesty in relationships, friendships, and business? It's easy, if you know how to spot the clues. Follow these tips to pinpoint 10 surefire signs of deception—and catch even the most slippery liar red-handed.

How to Catch a Liar

1. Inconsistencies. One of the easiest, and most reliable, ways to catch a liar is to identify inconsistencies in their story—details that just don't jive with common sense, prevailing logic, or societal norms. For example, if your date claims he's as rich as Bill Gates but drives a Hyundai, you can bet he's telling a tall tale.

2. Eye contact. When it comes to lying, the eyes can be a dead giveaway. Generally, liars avoid eye contact, but if you're dealing with a seasoned fabricator, he or she might stare excessively. In addition, most people's pupils dilate when they're lying because their adrenalin rises. According to an FBI Law Enforcement Bulletin, liars may also blink rapidly or close their eyes for slightly prolonged periods in an attempt to block out auditory or visual stimuli.

3. Contradictions. As they weave their tales of deceit, liars typically forget a few details along the way and reveal some telling contradictions. For example, if a friend backed out of your weekend plans because she supposedly had a life-threatening illness and later described the weekend as "wonderful," consider it a red flag.

4. Stammering or scrambling. The majority of liars, especially under questioning, will utter a lot of nervous ahhs, umms, and wells in an effort to buy time and save face. When confronted with particularly tough questions, they may also scramble for flimsy rationales and far-fetched excuses to reinforce the lie.

5. Changes in body language. There are a number of nonverbal cues that can signal deceit. Look for signs in the suspected liar's face that they're hiding, suppressing, or faking a spontaneous expression. And beware of those who touch their lower faces often, scratch their noses, or hide the hands behind their backs or in their pockets.

6. Shifting vocal patterns. According to experts, inconsistent vocal patterns are extremely common among dishonest people. In the midst of a lie, the pitch and tone of their voices may change on a dime, and the rate of their speech may suddenly slow down or get quicker.

7. Changing the subject. When trying to detect deception, watch out for this common tactic. For example, if you ask your boss about that raise she promised six months ago, and she starts to talk about the weather, you have to question her motives. After all, why would a liar subject herself to 20 questions when she can just pull a switcheroo?

8. Props. According to the FBI Bulletin, deceivers often use "soda cans, computer screens, and other objects, both large and small, to form a barrier between themselves and investigators." In addition, pay close attention if the suspected liar is playing with objects such as a purse or pen.

9. Inappropriate emotion. Beware of exaggerated emotion, anger, and defensiveness. (Remember former President Bill Clinton's finger-wagging, "I did not have sexual relations with that woman"?). Along these lines, claims of moral outrage and superiority can be a sure sign that something's awry.

10. Too much information. If a suspected liar's story is excessively detailed, it should make you doubly skeptical. Chances are, the liar is hoping they can cover all their tracks, leaving no room for doubt. It's especially fishy when too much information is given in response to an otherwise routine question like, "Where were you?"