When planning large-scale incidents or bombing campaigns, terrorists often conduct reconnaissance research to identify key targets. This may include taking photographs of potential target locations. Identifying an effective real-time method to distinguish between genuine photographers and those with more sinister intent may be beneficial for law enforcement and security agencies. Participants took photographs in a public place with a genuine intent (truth tellers) or sinister intent (liars). After taking these photographs, the participants were approached by an undercover interviewer (a mime artist) who asked them whether he could see the photographs. Later, the participants discussed their photographs in a formal interview. First, liars were less cooperative in their interaction with the undercover interviewer than truth tellers. Second, in the formal interview, liars mentioned some security features that appeared in the photographs more than truth tellers. The findings suggest that ‘using photographs to detect deception’ is a subject that could prove important to explore to benefit forensic and counter-terrorist practice.