Recent communication research shows several paths to improving accuracy in deception detection. According to truth-default theory, one promising approach is diagnostic questioning. A sample of elite U.S. Customs agents participated in a deception detection task. Agents viewed senders who were interrogated with one of three different sets of questions that differed in diagnostic utility. The different questioning sets produced a 36-point swing in accuracy from 42% to 78% accuracy. These findings demonstrate that how someone is questioned can make a substantial difference in deception detection accuracy and that improved accuracy is possible with diagnostic questioning.