Police Polygraph Test

Apr 20th, 2020

What is the police polygraph exam?

The polygraph is the technical term for what’s ordinarily called the “lie detector”. To become a police officer in the United States, you must pass the police polygraph exam; one of the most feared elements of the police test.

So, what’s involved?

The short answer is, it depends. Each police department has its own procedures and requirements. If you want to learn more about what’s involved in your own police polygraph exam, we encourage you to contact your local police department and find out what the standard procedure is.

That said, though, most polygraph examinations follow this format:

  • Pre-interview: here, you are asked questions before the polygraph exam has started. Often, candidates are required to document these answers on forms.
  • Polygraph exam: then, candidates are hooked up to the polygraph equipment and subject to the same questions. Often, the same question is asked more than one time, often up to 3-5 times, to ensure that the examiner has fully gauged the physiological response.
  • Post-polygraph phase: after the polygraph has ended, often examiners will talk to you about inconsistencies that came up. You may be asked to explain why some inconsistencies appear on 2-3 questions.


Police polygraph questions are asked as part of a wider background check. They are never used in isolation. It’s entirely possible that a candidate may appear to be telling lies but is, instead, telling the truth. Polygraph examiners are experienced in determining when a candidate is lying or when they are victims of either their own physiological responses or to the intricacies of the polygraph itself.

How does the polygraph work?

The polygraph measures the following physiological responses:

  • Heart rate
  • Blood pressure
  • Perspiration
  • Skin conductivity

When telling the truth, you are less nervous. Nervousness increases heart rate, blood pressure, perspiration, and skin conductivity. The more nervous answering specific questions over other questions, the more likely you are to be lying.

That’s the fundamental basis on how the polygraph works.

You may be asked two types of question:

  • Relevant – relevant to the concerns of the examiner, “Have you ever stolen anything?”.
  • Irrelevant – irrelevant to the concerns of the examiner, “Is today Tuesday?”

An irrelevant question may also include, “did you speak with the US president yesterday?”. Such questions may come across as unusual, but they are asked to serve as a “control” mechanism. Clearly, you did not speak with the US president yesterday. As a result, your body will react instinctively to say “no”, that did not happen.

But what if the next question was, “have you ever deceived a close friend/family member who was always good to you?”. In questions such as this, you are obliged to think – often hard and fast. Your physiological response will be very different to how you answered the previous question.

And that’s how the police polygraph exam works.

It takes two sets of responses and compares other, relevant questions, to those responses. If later in the exam you are asked, “have you ever taken drugs?”, your physiological response will be compared to how you answered the first two questions above. If your body reacts in the same way as one of the questions above, that alone will raise questions in the eyes of the examiner.

Depending on the system employed by the department, they may also format the test to encourage you to lie.

Take the following question:

  • “Have you ever lied in the first 20 years of your life?”

Clearly, everyone has lied. This creates two sets of responses:

  • First, that honest people find these questions more stressful to answer than liars. They are honest by virtue, yet do not want to admit they have been a liar. As a result, more honest people will react physiologically stronger than liars.
  • Second, that liars are more likely to react to “relevant questions”. We talked about relevant questions above, and now examiners may compare these answers with “irrelevant questions”.

The point here is this – that more pronounced physiological responses on a police polygraph test do not mean that a candidate is lying.

What matters is the system that the polygraph examiner has chosen to implement. As we have reviewed here, there are systems in which physiological provocations are intentionally sought to identify those who are honest and not the truth-deniers.

What police polygraph questions are asked?

Many police polygraph questions ask about drug use and/or theft. They are crime-specific questions and refer to the answers provided in the pre-interview phase and in other answers you provided during the initial application process. Background checks may also have been performed.

Examples of police polygraph questions asked include:

  • Questions of theft
  • Violence
  • Sexual misconduct
  • Misuse of drugs, including alcohol
  • Whether you have concealed any relevant, personal details
  • Financial misconduct
  • Criminal background checks
  • Falsification/lying by omission about application details

Of course, this is not intended to be an exhaustive list. But it gives you a concrete idea as to the type of polygraph question you can expect to be asked.

Other, more extreme questions may also be asked. For instance, there have been cases in which candidates have been asked, “Have you ever considered sexual conduct with an animal?”, or, “Have you ever been sexually inappropriate with a child?”.

Again, do not be alarmed by such questions. If you are telling the truth, there is nothing to fear. For as long as that is the bottom line, you will pass the police polygraph exam.

Is the polygraph accurate?

The polygraph is not really effective.

There is no exact science behind the polygraph. Studies vary on its effectiveness. The underlying theory of the process is sound. Most people, when lying, increase heart rate, blood pressure, perspiration, and skin conductivity.

The polygraph does not measure if you are lying, it measures physiological responses that may suggest you are lying. Ultimately, it comes down to the examiner as to whether he trusts your responses. It’s entirely possible, of course, that honest people fail the polygraph.

After all, the police polygraph exam is stressful. Candidates know that, even if they tell the truth, they may fail the exam. That stress alone is enough to trigger body responses that may not result if the questions were asked in a more relaxed environment.

It’s also worth noting that the most honest people around also tend to be more nervous and more anxious about the responses they deliver. They won’t want to deliver one word or syllable wrong. Just stuttering on a word that may inadvertently compromise the truth is enough to raise physiological alarm bells over the course of the exam.

Think of the polygraph as an indicator of truth, not a detector of it.

How to prepare for the police polygraph test

Police polygraph questions are not easy to prepare for.

It’s understandable why police test candidates find the exam stressful. Often the days before the exam are more stressful than the exam itself. To prepare for the exam, though, you need to be mentally equipped for the exam. Try to relax in the weeks and days leading up to the exam.

Learn how to relax.

Of course, we recommend that you do not lie to your examiner. Always tell the truth. There may be cases in which you have committed a small misdemeanor. However, lying may be considered a far greater misdemeanor. Your best bet, then, is always to tell the truth.

Think about body language, too.

As we have discussed, the polygraph exam is an indicator of the truth.

Examiners will use other methods to determine whether you are lying. One of those methods is body language analysis. Try to control your body language and not to conceal nor exaggerate your body movements. Questions on polygraph exams are often yes or no in nature. You do not need to react more than what’s required of you. Otherwise, it may raise unnecessary alarm bells.

Have confidence in your answers.

If you are honest, you should have conviction in your answers. After all, why would you be nervous about telling the truth? That makes no sense. Delete any uncertainty from your mind and enter the exam room filled with unbridled enthusiasm to tell the truth and get back home. The exam doesn’t need to be any more difficult than that. If you intend on lying, of course, that’s a whole different ball game.

If you are still unsure about how to answer police polygraph questions, we at Police Test Study Guide have put together a comprehensive program to help you through this often-stressful process. We help guide you through the process, the questions asked, as well as detailed body language techniques that deliver the most optimum impression.

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