While studying the faces of convicted killers, a Halifax psychologist says the truth about lies can be found in facial expressions.

Dr. Steve Porter, a forensic psychologist at Dalhousie University in Halifax, N.S., studies micro expressions and says the face of someone telling a lie is different from someone experiencing true emotion.

"People manifest particular concealed emotions, so how does that express itself on your face?" he told CTV.

Porter looks at emotions frame-by-frame and says it's nearly impossible for someone to mimic the complex muscle movements of such emotions as sadness, stress or despair.

Porter's research revolves around those who have publicly pleaded for the safe return of loved ones, but were later found to be the actual killers.

During his analysis, Porter highlights a particular area of the face, such as the eyes or mouth, and compares the area with a textbook example of someone experiencing a true emotion.

One such case study is Michael White, who was sentenced last year to life in prison for the murder of his pregnant wife.

Long before he was charged, White gave a tearful plea for his wife's return and his own innocence.

"My wife is a good person, never hurts anybody. If she's out there and you see me or you see this, just stay out there and we'll find you," White said.

After analyzing the footage, Porter concluded, "He's showing sadness in the mouth region, but not in the eyes or in the forehead region. In a complete sadness facial expression, we would expect that," Porter said.

"They don't seem to be sincere expressions of sadness," he added.

Porter revealed it was White's real emotions, which were exhibited at inappropriate times, that further led him to conclude he was lying about his wife's disappearance.

"He showed an anger expression in several occasions. Looking at this context, there should not have been displays of anger or disgust and that's what we were seeing."

While it has yet to be used in Canada, Porter's research has been sought out internationally for airport and border crossing safety.

The study of micro expressions is more than 40 years old and was originated by Dr. Paul Ekman in the United States.

Research shows that up to 60 per cent of people lie; males more so than females.

There are numerous physical cues associated with lying. People who aren't telling the truth have a tendency to lean forward more, will lick their lips, handle objects and avert their eyes.

Raising a hand to the nose has also been associated with lying. Scientists say this is due to the engorgement of erectile tissue in the nose that occurs when someone tells a fib.

Verbal cues can also give someone away who is trying to get away with mendacity. Clearing of one's throat, stuttering or not using contractions (such as saying did not versus didn't) are all cues that someone is trying to pull the wool over your eyes.