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Roger Clemens licks his lips. But does that mean he's lying?

Baseball hero Roger Clemens swore under oath during a grueling Congressional hearing Wednesday that he didn’t use steroids during his phenomenal baseball career. “I’ve been accused of something I’m not guilty of,” he defiantly told committee members. His words may have denied the claims by his former personal trainer, but his body was saying something else. At least that’s what one body language expert thinks.

During the 4½-hour hearing, Clemens was agitated, he didn’t make direct eye contact with the committee members and he even stumbled over the name of Brian McNamee, his chief accuser.

“The body doesn’t lie, the voice doesn’t lie,” Lillian Glass told NBC’s Peter Alexander Wednesday during the hearings. “When you look at Roger Clemens, you see a lot of lip licking… It’s very consistent. He’s very nervous….You see a lot of wrinkling of the forehead. He looks down. He’s disconnected. That makes you question what’s really going on with him.”

Jonathan Ernst / Reuters
Former New York Yankee pitcher Roger Clemens couldn't keep his tongue in his mouth while testifying before Congress.

Glass was all praise for McNamee, who sat at the same table.

“McNamee was forward. He was ready. He was receptive … not defensive. He looked right at the people who were questioning him. He wasn’t nervous.” WATCH THE VIDEO

Glass claims that when people are lying they move their shoulders, clench their jaws, lick their lips and shuffle their feet.

But does showing anxiety really go hand-in-hand with lying? It’s popular to talk about a person’s shifty eyes or to assume that when someone is fidgety or nervous that they’re not telling the truth. Dr. Simon Rego, licensed clinical psychologist at Montefiore Medical Center in New York isn’t so sure.

“Certain movements or gestures like those may be more of an indication of anxiety or nervousness than lying per se,” says Rego. “This type of lie detection seems analogous to polygraph tests. They don’t really detect when someone is lying as much as when they are anxious.”

Other experts say that tone of voice is more revealing than eye contact, although people who are telling the truth often stumble over their words. It’s the practiced liar who tends to be the smooth talker, they say.

No one would accuse Clemens of being a smooth talker under questioning. His career is on the line, and as he said during the hearing, “I’m never going to have my name restored.”

Still, it’s not only the body language experts who didn’t believe Clemens. Just 1 in 5 msnbc.com readers think the Rocket is telling the truth.