In this experimental study, we report the effectiveness of a forced-choice testing (FCT) technique for detecting deception in a mock counter-terrorism scenario. Participants were randomly assigned to one of three conditions: ‘witnesses’, ‘terrorists’, or ‘innocent individuals’. Participants in the witness and terrorist conditions read information regarding a planned terrorist attack. Innocent individuals did not read this information and were told they were suspected of being terrorists. Next, all participants were asked to complete the FCT which consisted of 20 questions (16 target-items and 4 distractor-items). For each question, individuals were forced to select one of four possible answers – one of which was the correct answer – whilst being timed. Terrorists were expected to be deceptive and avoid the correct answers, thus score below witnesses, innocent individuals, and chance. Overall, performance on the FCT revealed significant differences between the witnesses and the terrorists. As expected, witnesses gave more correct answers and responded more quickly. All this would be positive support for using the FCT if it were not for innocent individuals scoring at a similar rate to terrorists and taking longer to respond. Taken together, the implication of this is that FCT may misidentify innocent people as terrorists.