It’s not always easy to recognize when your guy isn’t telling the truth. Not every lie makes beads of sweat roll down his forehead or forces him into a rambling story; nor will his nose grow. But there are subtle cues that indicate he’s trying to fudge the facts. To help awaken your inner lie detector—and prevent dishonesty from floating in your marriage—we called in ex-CIA polygraph examiner Dan Crum, author of the new book, "Is He Lying To You?" (www.lyingbook.com).

At one time or another your guy has probably said something that sounded a little fishy. The bachelor party ended at 10 p.m.; the auto mechanic made him invest in a bigger engine; he’s allergic to opera. In fact, men tell twice as many lies as women, most of which are just little white lies, according to a new survey from 20th Century Fox to mark the DVD launch of TV series "Lie To Me."

"Men lie to preserve their ego," Crum explains. "They don’t want to spoil the reputation they’ve worked hard to earn." So if he wants you to think of him as reliable, he may fib that he made that phone call to the insurance company a week ago—and then make a note to do it tomorrow. Other times, lying is simply the easy way out—especially if he thinks the truth will get him in trouble, Crum says. Maybe he drove his female coworker home because her car broke down, but tells you he drove home alone so you won’t get worked up.

Even though small fibs seem harmless, these little white lies can undermine a sense of trust in your marriage. "When men get away with small, insignificant fibs, it builds their lying comfort level," Crum says. "The more practice he gets, the higher your risk that he’ll lie about bigger things down the line." But you don’t need to hook him up to a polygraph machine to pick up on deception. These simple tactics can help you spot the lie, get him talking truthfully, and pave the way for a more trusting and honest relationship.

Take a mental picture of his usual behavior. The way your guy behaves verbally and non-verbally when he’s relaxed is what Crum calls a man’s WIN (what is normal). The next time you and your husband are talking about the weather, plans for the weekend or any other no-pressure topic take note of his WIN—does he clear his throat or gesture when he speaks? Only when you know his WIN will you be able to pick up on the subtle changes in body language, speech, and tone of voice that occur when he’s trying to hide something. Also, knowing that he normally fidgets with his wedding ring or bites his nails will ensure that you won’t confuse his typical habits with deceptive behavior.

Watch his posture. You can notice the first sign of deception by watching how your guy’s body reacts to a question. "When a man is at ease, he typically sits back in the chair, rests his hands on his legs or the arms of a chair, and crosses his legs," Crum says. These restful positions are called his sleep points. A question that he feels is threatening will cause those sleep points to "wake up." You’ll notice him sit up, lean forward, uncross his legs, or display a new hand gesture. "Our bodies are wired with an autonomic nervous system, which involuntarily responds when we’re put under pressure," Crum explains. "There’s no controlling it." But if the question doesn’t cause him stress, his nervous system won’t react, and his sleep points will remain in the same position.

Ask the right questions. If your guy gave you reason to suspect he is lying and you want the truth, know that the way in which you question him can make or break his admission, says Crum. Let’s say you ask your husband if he enjoyed the lunch that you packed him for work. If he says yes, but based on the reaction of his sleep points you feel like he’s lying, your best strategy is to drop the subject for now. "If you accuse him of lying or bombard him with questions, he’ll either go on the defensive or continue lying," Crum says. "Plus, he’ll be more on guard next time you bring it up." Instead, give yourself time to find evidence that he’s lying or think about how you want to approach the subject next time. Then, try one of these questioning strategies:

Ask an assumptive question: If you think your husband is being untruthful, you can turn that assumption into a question. In this case, you might assume that he went out for lunch and ask: "Where did you end up going for lunch yesterday?"

"This creates the opportunity for him to acknowledge the truth without feeling pressured," Crum explains. "Plus, because the question forces him to come up with more than a yes or no response, it may be easier for him to come clean rather than think of an answer that makes sense."

Use a bait question: If you find evidence of deception—maybe you found the bag of lunch in the back of his car or a receipt from the pizzeria near his office—you can use that evidence as bait to force your guy to give an explanation. Try: "Is there any reason why there’s a receipt for $10 from the pizzeria yesterday?"

By asking about the evidence—not pointing fingers—he doesn’t feel personally attacked, which makes him more likely to be honest. And maybe he’ll admit that he doesn’t really like tuna casserole—even if it was packed with love.