This experiment was designed to assess, for the first time, the effects of training police officers, social workers and students in Criteria-Based Content Analysis (CBCA) in an attempt to increase lie detection accuracy. A within-subjects design was implemented. Participants rated the truthfulness of a maximum of four statements before training in CBCA and rated the truthfulness of a different set of four statements after training. The raters were only exposed to the written transcripts of the communicators. Two thirds of the statements utilized were truthful and one third were based on fabrications. Before training, there were no significant differences in detection accuracy between the police officers (66% accuracy), the social workers (72% accuracy) and the students (56% accuracy). After training, the social workers were 77% accurate and significantly more accurate than the police officers (55%) and the students (61%). However, none of the three groups of raters significantly improved their lie detection accuracy after training, in fact, the police officers performed significantly poorer. Overall, police officers were significantly more confident than social workers and lay persons regardless of accuracy. Further, participants were most confident when labelling a statement truthful regardless of whether or not this was the correct decision.