Comparison of Polygraph Data Evaluation Conventions Used at the University of Utah and Department of Defense Polygraph Institute

• NCJ Number: 226987
• Journal: Polygraph Volume: 38 Issue: 1 Dated: 2009 Pages: 106-114
• Author(s): Stuart M. Senter; Andrew B. Dollins; Donald J. Krapohl
• Date Published: 2009
• Length: 9 pages
• Grant Number(s): DoDPI97-P-0005
• Sponsoring Agency: US Dept of Defense Polygraph Institute
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

This paper reports on a project conducted to identify factors that can explain why the accuracy for specific-issue laboratory polygraph studies based at the University of Utah (U of U) is approximately 12-percent higher than for similar studies conducted at the Department of Defense Polygraph Institute (DODPI).

Abstract

Results from the current study suggest that, at least for laboratory data, the difference between the U of U and DODPI veracity-decision accuracies are likely not due to the institute-specific guidelines used to assign values to physiological responses. Rather, the differences are likely due to the data evaluation conventions used to make a decision after the values are assigned. There was a clear 16-percent increase in correct decisions when using the U of U evaluation conventions relative to the DODPI evaluation conventions. Other factors that were not investigated could also contribute to the observed discrepancies found in other studies. These include such factors as participant characteristics, participant manipulation methods, and the physiological tracing quality. These findings have two implications. First, the accuracy differences between the DODPI and U of U may be attributable to decision conventions that follow the scoring of the physiological data, and not differences between the scoring systems used at the two institutions. Second, resolving “no opinion” (NO) decisions by increasing the number of question series asked produced the greatest increase in accuracy, with the three or five question series producing an 11.4-percent increase in accuracy over the three-question series. Use of the total-scoring rule compared to the spot-score rule also produced a significant increase in accuracy, albeit to a smaller degree (2.8 percent). This study collected data from 50 deceptive and 50 nondeceptive participants; they were evaluated by 4 different scorers. Two of the scorers used the U of U scoring system, and two used the DODPI scoring system. 4 tables and 30 references