We examined whether speech‐related differences between truth tellers and liars are more profound when answering unexpected questions than when answering expected questions. We also examined whether the presence of an interpreter affected these results. In the experiment, 204 participants from the United States (Hispanic participants only), Russia, and the Republic of Korea were interviewed in their native language by a native‐speaking interviewer or by a British interviewer through an interpreter. Truth tellers discussed a trip that they had made during the last 12 months; liars fabricated a story about such a trip. The key dependent variables were the amount of information provided and the proportion of all statements that were complications. The proportion of complications distinguished truth tellers from liars better when answering unexpected than expected questions, but only in interpreter‐absent interviews. The number of details provided did not differ between truth tellers and liars or between interpreter‐absent and interpreter‐present interviews.