Interpersonal deception theory (IDT) frames deception as a communication activity and examines deception within interactive contexts. One key element of the theory is the role of suspicion in prompting behavior changes. An experiment testing several suspicion-related hypotheses paired participants (half friends, half strangers) for interviews during which interviewees (EEs) lied or told the truth and interviewers (ERs) were induced to be (moderately or highly) suspicious (or not). Results confirmed that suspicion and deceit were perceived when present, suspicion was manifested through nonverbal behaviors but with different behavioral patterns for moderately versus highly suspicious ERs, and suspicion affected sender behavior. Relational familiarity moderated some behaviors. Results are discussed in terms of mutual influence processes and the dynamic nature of communication in interpersonal deception.