Impact of Prior Knowledge From Participant Instructions in a Mock Crime P300 Concealed Information Test

• NCJ Number: 249355
• Author(s): Michael R. Winograd, J. Peter Rosenfeld
• Date Published: December 2014
• Length: 9 pages
• Agencies: NIJ-Sponsored
• Award: Countermeasure Mechanisms and Ecological Validity of P300-Based Concealed Information Tests

Annotation

This study tested the hypothesis that participant exposure to crime details in mock crime scenarios would bias detection rates toward enhanced sensitivity.

Abstract

In P300-Concealed Information Tests used with mock crime scenarios, the amount of detail revealed to a participant prior to the commission of the mock crime can have a serious impact on a study's validity. The current study used a 2 x 2 factorial design in which participants in a mock crime scenario were either informed (through mock crime instructions) or were naïve about the identity of a to-be-stolen item, and then either committed (guilty) or did not commit (innocent) the crime. Results showed that prior knowledge of the stolen item was sufficient to cause 69 percent of innocent–informed participants to be incorrectly classified as guilty. Further, the study found a trend toward an enhanced detection rate for guilty–informed participants over guilty–naïve participants. Results suggest that revealing details to participants through instructions biases detection rates toward enhanced sensitivity in the P300-CIT. (Publisher abstract modified)