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Detecting Deception: Speech and Voice as a Lie Detector

by | Jul 6, 2018

Written in collaboration with Janine Driver, author of You Can’t Lie to Me

Once we’ve established the baseline, it’s time to drill down to expose the meaning behind the words. While body language has long been the focus of detecting deception, research has shown that the analysis of a person’s speech may be much more accurate than merely observing non-verbal behavior.

No matter the lie, there will always be verbal indicators of deception lurking in the tone and speech a liar uses.


The tone of a person’s voice has an amazing effect on us. Singing a request versus shouting it in an exasperated voice can have a direct effect on trust.

Think about it: how many times have you gotten what you wanted when you used a buttery voice? You will almost never get what you want with an angry voice, unless you are trying to strike fear in someone.

Vocal tone is a powerful indicator of emotion – research has shown that a person’s vocal tone will waver from the baseline in up to 95 percent of all deceptive statements. It’s one of the most reliable indicators of deception, and whether it goes up or down depends on the emotions involved.

  • Vocal tone rises when we are angry or excited. You might see this when your subject is trying to convince you of something. Be careful, though – a truthful person will also get angry when wrongfully accused. The difference? The liar’s anger subsides more quickly.
  • Vocal tone lowers with sadness and shame. When your subject’s voice gets lower, pay close attention.


Mastering the art of detecting deceptive speech is best learned through Statement Analysis – a system of analyzing the grammar and logic of words that come out of our mouths. Often the inconsistencies of a story can be picked up almost entirely from shifts in tense or word choice.

Picture this:

A liar is like a tightrope walker whose goal is to get across the canyon of your doubt and skepticism to freedom when they have convinced you of their tale. Their challenge is to remain upright and make steady progress throughout the interview. As the interviewer, your job is to watch for their imbalance or leaks of deception along their journey.

The extra baggage of deceit can be burdensome. This baggage includes:

  • The truth: the facts as they really happened
  • The “facts” in their own lie
  • What they’ve told you in previous conversations
  • The new “facts” they are feeding you
  • The fear of the unknown: what you know but haven’t disclosed
  • Your reaction to their tale

The extra baggage of deceit is likely to throw the liar off balance, triggering their fight or flight instincts.  Pay close attention, as this baggage creates three different categories of signals that can reveal your subject’s stress response and suggest there’s more to the story:

1. The Equivocator: the main balancing act. Consider the gymnast on the balance beam who might suddenly throw a leg out to one side to compensate for weight shift on the other. You will hear this same kind of equivocation when people are lying. Their speech wavers, deviating from its normal pattern and shifting in odd, uncharacteristic ways.

The equivocator will leak inconsistencies in many of their statements or try to make everything seem like sunshine and roses – liars don’t like to talk in the negative. If their answers don’t relate      to the question, or if their language is garbled or deviates from the baseline, it is cause for an amplifying question.

     Mixed-up tenses – When your subject recounts a story, pay close attention to the tenses they use – sometimes they will switch tenses in the middle of the story.

     Double-talk – Remember that it’s human nature to tell the truth. Because our brain is wired to tell the truth, when we lie, we may often say things in a strange way.

     Entering the Twilight Zone – This involves a variation on “one thing led to another,” using opaque language.

     Frequent pausing – When there is a dramatic pause at an inappropriate moment, your subject may be thinking of the word they want to say and then gathering another word instead.

     Start-Stop sentences –  Start-stop sentences occur when your subject realizes they’re about to tell you something they don’t want to tell you.

2. The Maximizer – the classic “fighter”.  The maximizer will try to overwhelm you with brute force language or nonsensical details. Honest people convey information, while liars try to convince.

3. The Minimizer – the classic “flighter”. The minimizer is reticent and subconsciously disappears into themselves in an attempt to avoid the truth and retreat from the conversation.

In forensic investigations, we look for deviations from normal behavior to catch a fraudster in the act. While speech and voice can help with deception detection, when combined with fleeting non-verbal cues like micro-expressions – the smallest and quickest of facial expressions – they can create a hotspot for a deeper dive.

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