NCJ Number
211799
Journal
Polygraph Volume: 34 Issue: 3 Dated: 2005 Pages: 184-192
Date Published
2005
Length
9 pages
Annotation
Polygraph scores from four research projects were used to compare a proposed set of Evidentiary Decision Rules and traditional Investigative Decision Rules in polygraph testing based on correct decisions and the balance of errors.
Abstract
Two types of decision rules were applied to the polygraph scores. The first type consisted of traditional rules used for polygraph examinations by the Federal Government, called Investigative Decision Rules in this study. According to these rules, a call of "deception indicated" (DI) is made when the total of all scores is -6 or below, or if the sum of any one of the relevant questions is -3 or lower. Decisions of "no deception indicated" (NDI) require a positive total score for each relevant question and a grand total of +6 or greater for the sum of all spot scores. All other cases involve inconclusive decisions. The second type of decision rules, referred to as Evidentiary Decision Rules in this study, begins with asymmetric cutting scores; if the grand sum of scores is -6 or lower, the call is DI; if the grand sum of all scores is +4 or greater, the call is NDI. In those cases in which the grand sums range from -5 to +3, the "sport score rule" (SSR; Light, 1999) is applied. For these cases, if a single relevant question has a sum of -3 or below, the decision is DI. All other cases are called inconclusive. In the current study, Evidentiary Decision Rules were found to produce more correct decisions, fewer inconclusives, and a more balanced accuracy than the traditional Investigative Decision Rules. This suggests that Evidentiary Decision Rules may be better for courtroom and paired-testing (Marin Protocol) settings. 2 tables, 1 figure, and 17 references