"When someone has a lot of charisma, friendliness, attractiveness and power, we tend to disregard any lying or deception," she said. "We don't even see it."
But "intoxicating" as a speaker can be, Wood said, that person can also make mistakes that will poke holes in the legitimacy of the speech.
"One of the deception factors to look for in these kinds of conventions include where the speaker is looking when he is speaking," said Wood, who is not attached to the presumed Republican presidential nominee John McCain or the Democratic nominee Barack Obama.
"Notice whether someone looks straight forward when they say the most important statement," she said, adding that she has noticed that Obama often looks off to the side during his speeches.
Blinking, said Wood, especially when a speaker begins to do so at a faster pace, is often a sign of waning confidence.
"Frequent blinking would indicate that they don't feel comfortable with their statement," Wood said. "The timing is the tell: If a person's blink rate goes up drastically during one part of their speech, that would send a certain message."
It may seem minute, but even the way speakers interact with the podium can say a lot.
"Look for where their hands go on the podium as they are saying certain messages," Wood said. "If they grip the podium tightly when they say certain things, they may be indicating that they don't feel good about what they're saying. If you feel good and honest, your hands usually come up and open."
Wood criticizes McCain's tight grip of the podium, which, she estimated, he does "to keep his anger down but still appear energetic."
Body language expert Hogan said that the speed at which someone talks can also indicate how truthful the speaker is.
"When McCain is most genuine is when he speaks slowly and thoughtfully," said Hogan, who said he's a libertarian and does not support either candidate.
"When he gets rattled, his voice raises up in pitch and he'll sort of speak in spurts," Hogan said.
Pitch in voice is an issue onetime Democratic presidential hopeful Hillary Clinton battled with quite a bit, according to Wood.
"If a person's voice goes high on certain words, listeners become skeptical," she said. "Hillary's biggest tell was her voice, but really, almost everyone when they're under stress sees their voice go up [in pitch]."
Democratic vice presidential nominee Joe Biden lowered his voice several times during his speech Wednesday night, a technique Hartley said is a sign of a great speaker.
"It's a great technique; the quieter you get, the more important the information is," Hartley said.
"We tell secrets in very low tones so it's a good communication tool," he said. "People listen more intently when people speak softly."
And as Americans get ready to watch Obama speak and officially accept the Democratic Party's presidential nomination tonight in Denver, Hartley has some advice for viewers: No matter how captivating the speech, pay attention to the way he moves.
"When in doubt, trust his body language."