Can you use a lie detector in court?
Juries tend to overestimate the reliability of lie detectors, even when told of their actual accuracy. For that reason, it is considered prejudicial by the courts, since it’s probative value is too low to outweigh the odds of it’s misuse. Hence it is not permitted. If they come up with a better lie detector (the new Functional MRI systems are controversial, but if they eventually prove to be accurate enough, that may be an example) or if the public in general learns to better understand their degree of accuracy, courts may change that opinion, but as of today, I don’t know of any US court system that allows them. Lie detectors are, however, a valuable investigative tool because police have enough experience with them to allow them to help focus their investigation.
