In a recent training course for investigators conducted for the Calgary Police Service, Dr. Ed Geiselman, a UCLA professor and a member of the Force Science Certification Course training staff, included a block on detecting deception. One tip he suggested is to pay close attention to the pacing of a subject’s answers and to see if you notice dramatic fluctuations in speed. If you do, you might be on to something.
Geiselman explained that it’s possible that if someone slows way down during the initial delivery of answers — particularly answers to incident-critical, “hot button” questions — then proceeds to noticeably pick up verbal speed, then ends up slowing down again until he gets into the next answer, he may be unintentionally showing you that he’s actually grasping for “mental traction.” It’s possible that his slow pacing demonstrates the fact that he’s thinking and trying to develop an answer, then as his idea of an answer crystallizes, he feels more comfortable and begin to pick up the pace.
Geiselman cautions that this fast-slow-fast-slow verbal pacing isn’t sufficient evidence on its own to say that the subject is definitely trying to deceive you, but it’s a possible indicator you should note.