Anxiety occurs for multiple reasons, so false positives would always be a confounding factor, even if micro expressions occured 100% of the time. There is quit

Anxiety occurs for multiple reasons, so false positives would always be a confounding factor, even if micro expressions occured 100% of the time. There is quite a bit of evidence that even with physiological measures linked to stress and lie detector machines, there is little reason to believe lie detectors are especially effective. Given that non invasive means of detecting anxiety are limited, and anxiety is itself limited, such screening is going to not be helpful. That said, there are some great studies on using recognition and EEGs or fmri machines to detect lies. Your brain processes item's you recognize in different ways, so if someone maintains they never were in an apartment where a murder occured nor had seen it ever, you could display a series of apartments, including the murder scene, and be able to tell when they recognized the apartment. It's known in the field as the Guilty Knowledge Test, or GKT. Check out the work by Farwell and others if you are interested.