In order to identify the effectiveness of the cognitive interview in interrogation, a natural field experiment was conducted. During a lecture, a man unfamiliar to the 30 students entered the auditorium and began to argue with the lecturer. The students were not instructed to remember what was happening, nor were they aware that the conflict had been artificially staged. Eight months later, the students were questioned about the stranger’s appearance: the first group (15 people) was interviewed using the standard police interrogation method, and the second group (15 people) using the cognitive interview method. One week later, the first group was interviewed again using the cognitive interview method. The effectiveness of the standard police interrogation, the cognitive interview, and a combination of the police interrogation followed by the cognitive interview was compared. The most complete verbal description based on 12 specified features, as well as the best photographic identification, were provided by witnesses who underwent the police interrogation followed by the cognitive interview.