Background: Finding methods for lie detection is one of the main concerns in human Societies. The aim of this study was to design a system to evaluate the arterial photoplethysmograph signal in polygraph system and submit it as a new signal on the polygraph.

             Methods: The data set included psychophysiology signals and was done through an inductive test and by using classic polygraph device in two groups. After recording the signals, the signals noises were removed and time features were extracted. Statistical analysis was done by ANOVA and T-test. Consequently data were classified and accuracy coefficient was calculated by applying these features to Linear Discriminate Analysis LDA. All data processing was done in MATLAB software.

             Findings: 20 men participated in the study. The results showed that changing of arterial photoplethysmograph signal has significantly reduced in target question (P=0.022) and it could create a higher accuracy in lie detection.  By combining signals and using arterial photoplethysmograph, the best results were obtained and the accuracy was calculated as 81.33%.

             Conclusion: by replacing a new signal in this study, the percentage of accuracy was calculated comparable with other methods of polygraph. So this new method can be suggested for use as a lie screening system.