How can you tell your girlfriend is lieing?

dude,

love is patient, love is kind, love is generous..

love is a lot of stuff

but not jealousy. leave her if you can't trust her. you will only cause more problems.

All of the answers are interesting and might apply some of the time, but not all of the time. The fact is you can't tell for sure if she is lying. If she has a history of lying to you or if her behavior has suddenly changed then I understand your concern. If not, ask yourself if she has ever given you a reason not to trust her or if you are just being suspicious with no basis.

Her lips are moving.

I agree with Cosreal, many times the man is just overly jealous and will cause even bigger problem. Sorry but seen this many time already and it never turns out good. Lie detectors are not reliable and if you just want to know if she's lying then listen to sellyourfoot. But really must work on the trust issues.

What is Lieing?.....Do you not mean.... L Y I N G???

Women are way more talented at deception. But, they hate confrontation and that is one of their weaknesses. Some women hold their own better than others, but, for many their "tell" is acting OVERLY offended by the suggestion or accusation you make. She may not admit to lying but at least you will know she is and plan accordingly. The best way is to simply verify by checking her stories and/or snooping. There's another situation. If her reaction to the slightest curiosity by you or the slightest snooping is "over the top", she's probably getting nervous about being caught in her lies.

lie-detector, have someone spy on her. getting to the thruth isnt always pleasant.

When I lie to my boyfriend, the name of the game is "avoidance." If he asks me a question and I can't get out of answering, I'll put him on the ropes by answering with another question. Example:

"Where were you tonight?"
"Why does it matter?"

I will also try to downplay my responses and never make a big deal out of anything. Even if he is getting close to the truth, I don't sweat it because he has no proof. I just play it cool, act bored and slightly annoyed and don't give anything away.

If this is not how your girlfriend acts, some common facial indications that someone is lying are:

Too much (forced) eye contact. This is due to the bogus myth that liars will never look you in the eye.

Looking off to the right when trying to "recall" a memory. This is a surefire way of spotting a lie. The right side of the brain is the "creative" side, whereas the left side is the recall side. When recalling a genuine memory, we look off to the left, when making up bullsh*t, we look off to the right.

Any sort of fidgeting like tugging on earlobes, scratching the back of her neck, biting her lip, wringing or stroking her hands, playing with her fingers are all obvious indications of deception.

Good Luck