Will lie detectors ever be 100% accurate?

Kozel and his team initially identified typical neural activity patterns for true and false statements. Then, in the first use of fMRI to detect deception in individuals, the researchers used the patterns they identified to correctly determine whether each of the subjects had taken a watch or a ring 90 percent of the time.
The use of fMRI represents the cutting edge of lie-detection technology. As far as we know, no region of the brain specializes in lies. But investigators have found that lying activates brain regions involved in suppressing information and in resolving conflicts—such as that between the impulse to describe reality and the wish to contradict it. The use of fMRI combined with a clever questioning strategy could lead to a better method for detecting lies or, more precisely, for getting at the truth despite a person’s attempts to hide it.
Improved ability to detect falsehoods would be of significant use in solving crimes, for example, and perhaps also in ferreting out military spies. Unraveling the neurocircuitry of deception, moreover, might help doctors better understand, diagnose and treat patients with disorders in which compulsive lying is a prominent component, including antisocial personality disorder and substance dependence.

Link: http://www.sciam.com/article.cfm?id=building-a-portrait-of-a-lie