Abstract
Lie detection based on nonverbal behavior is not a standard method, it is an intuitive process, applied by lay persons, but also professionals. The levels of success are usually around the level of chance.
The main goal and research question is to find out: what is the success rate of differentiation between lies and truths in this specific professional group of Czech population, is it the same or different from the results reported in the context of available resources. The research will focus on the ability of respondents to determine the truth or deceit on the basis of non-verbal and paraverbal expressions of observed subjects, with focus on specific professional groups - mainly police workers.
The procedure: The material consisted of short video sections originating from real investigation of serious crime. After the pilot study the stimuli material has been created consisting of 21 video-sections lasting 30 seconds, the sound of the videos was filtered, so the paraverbal characteristics were maintained, but the content of the speech was unclear.
The research sample consisted of 197 police officers from 5 departments. Selected results: The TRUTH detection accuracy - (the accuracy of correct evaluation of the truth-telling people on the video) was situated between 0,25 (25%) to 0,75 (75%).
The LIE detection accuracy - was situated between 0,44 (44%) to 1 (100%). The overall accuracy (means combined accuracy of lie and truth detection) was situated between 0,33 (33%) and 0.86 (86%).
The discussion: The results indicate that (among others) we can find so called lie bias among the police workers. The main limit of the study is probably the lack of repeated retest of the sample.
This and other findings were involved into the police training focused on communication and lie during criminal investigation, which is not systematic in Czech Republic. The plan is to test also other professional groups in the future.