A non-standard method for estimating accuracy of lie detection techniques demonstrated on a self-validating set of field polygraph examinations

A unique method for estimating field accuracy of the Comparison Question Test (CQT) – a polygraph technique – is presented, based on a combined probabilistic and algebraic model. It is built on paired examinations in criminal cases in which two opposing versions per case have been subjected to polygraph tests. The developed model is ground-truth free, thus there was no need to rely on external criteria of deception (e.g., confessions or physical evidence) in estimating the accuracy of the CQT. Results indicate an accuracy rate of 0.94 in detecting guilty examinees (Sensitivity) with a 0.06 False Negative rate and an accuracy rate of 0.835 (Specificity) with False Positive of 0.165 for the innocents. These figures excluded 20% of the cases that were ruled inconclusive. When no inconclusive calls were allowed, the accuracy rate dropped down to 0.8 with 0.2 error rates for both the guilty and the innocent examinees. The importance of this research stems from its being a field study that due to the unique methodology was not subjected to weaknesses usually found in polygraph field validity studies. This method is applicable to other techniques of deception detection and with some necessary adaptations may be also to eyewitness situations.