Private Polygraph Tests in California Criminal Cases

Updated

Defense lawyers use “private polygraph tests” to exonerate clients

More info at http://www.shouselaw.com/private-polygraphs.html Most people think of polygraphs (lie detectors) as something that the police do. But defense lawyers can do them too, often with great success. In this video, a California criminal defense lawyer discusses the use of private polygraphs in cases involving allegations of child molestation (child sexual abuse or lewd acts with a child under 14). A private polygraph involved having the client sit for a secret lie detector examination with a defense polygrapher. If the test results indicate the client is being truthful in denying the allegations, then we can turn that over to the district attorney and often it will persuade them to dismiss the charges. On the other hand, if the client “fails” the polygraph examination, we can simple shred the results and never have to disclose them to anyone. A good criminal defense attorney will use private polygraphs as a tool any time his client adamantly denies the allegations of child molestation. They can help to exculpate the client and prevent innocent people from being wrongfully convicted.


A private polygraph test is when a person hires a polygrapher and voluntarily takes a lie detector test in order to demonstrate that he or she is being truthful about a matter. This is frequently done in criminal cases to exonerate a defendant.

The examiner asks subjects whether they committed the crime. If they answer no and the test indicates truthfulness, these results can be given to the prosecutor in the hopes of getting the case dismissed. If the polygraph indicates the subject is being untruthful, then the test and the results are kept secret. 

A lie detector test and a polygraph test are the same thing. A polygraph is an electrical device that measures biological changes in people when they answer questions. These changes can indicate when someone is being deceptive.

Studies have shown that lie detector tests are not reliable all of the time. Because of this, test results are not admissible as evidence in a jury trial. This is unless the prosecutor and the defense attorney both agree to have the results admitted.

It might be strategic for a defendant to take a private polygraph in three situations. These are when it is used to:

  1. try and get a charge dismissed during the pretrial process,
  2. persuade a prosecutor to agree to have the state conduct a follow-up test, or
  3. convince the defendant to enter into a plea bargain, or plead no contest.

Note that a defendant can take a private polygraph test even if he/she is in jail. In this scenario, the defendant's attorney would need to:

  • obtain a court order for the test, and
  • plan with the county jail, or state prison, to have the test taken.

Trained polygraph examiners administer lie detector tests for a fee. The typical cost is between $200 and $2,000.

Our California criminal defense attorneys will discuss the following in this article:

private polygraph test
A private polygraph test is when a private polygraph examiner conducts a lie detector test.

1. When is a private polygraph a good defense strategy?

A private polygraph test is a good defense strategy in three situations. These are when it is used to:

  1. convince the prosecutor to dismiss a charge,
  2. convince the state to conduct a follow-up polygraph of its own, or
  3. convince the defendant to enter into a plea bargain.

1.1. Dismissal of charges

This strategy requires that a defendant take a private polygraph test early in a case. Often, it gets taken during the pretrial process or even before charges are filed.

If the test results indicate the accused is telling the truth about not committing a crime, then:

  • the defense lawyer may approach the prosecutor, and
  • reveal the test results to demonstrate the accused is factually innocent.

Here, the prosecutor may find the results compelling and agree to dismiss any charges in the case. Prosecutors generally do not want to pursue charges against a person they have reason to believe is factually innocent.

If no dismissal, the prosecutor may decide to reduce a charge to a lesser offense.

1.2. Persuade a prosecutor

There are times when:

  1. a private polygraph shows the possible innocence of a defendant, but
  2. the prosecutor ignores the results and presses on with the case.

In this situation, it is an effective strategy for the defense attorney to:

  • approach the prosecutor again, and
  • offer to have the defendant take a second polygraph, given by the prosecutor's office.
The prosecutors may have more confidence in their own polygrapher. If both the defense and the state's polygraphers agree that the defendant is being truthful, the prosecutor is more likely to defer to the tests and dismiss the case. 1

 

1.3. Plea bargain

There are times when a defendant:

  1. takes a private polygraph test, and
  2. the results imply that he committed the crime in question.

In this event, the defendant may want to think about entering into a plea bargain. This means to plead guilty or no contest to the crime charged or to a reduced charge.

This strategy avoids the risk of:

  • the accused going to trial, and
  • being found guilty on the greater charges.

2. If a defendant fails the test, will the results go to the authorities?

If an accused fails a private polygraph test, the results do not have to go to the:

  • police, or
  • prosecutor.

The defense attorney can simply never come forward with the fact that a polygraph was ever administered.

This is what makes a private polygraph “private.”

courtroom discussion about private polygraph test
The law says that the results of a polygraph test can only be used as evidence if the prosecution and the defense agree that this is okay.

3. If the defendant passes the test, can that be used as evidence in court?

The law says that the results of a polygraph test can only be introduced as evidence at trial if:

  • the prosecution and the defense agree,
  • to its admissibility.2

The same rules apply to the following pieces of information:

  1. the opinion of a polygraph examiner,
  2. the fact that the defendant (or a witness) offered to take a polygraph test,
  3. the fact that the accused (or a witness) refused or failed a test, and
  4. the fact that a party took a polygraph test.3

4. What if the defendant is in jail?

A defendant can take a private polygraph test even if he/she is in jail.

In this scenario, the defendant's attorney would need to:

  • obtain a court order for the test, and
  • plan with the county jail, or state prison, to have the test taken.

5. Does a defendant have the right to present lie detector results as exculpatory evidence?

A defendant does not have a constitutional right to present lie detector results as exculpatory evidence.4

Note two things:

  1. exculpatory evidence is evidence that clears a defendant of guilt, and
  2. the U.S. Constitution says a defendant has a right to present a defense.5

Despite the above, the Supreme Court has ruled that an accused does not have a constitutional right to introduce lie detector results into evidence.6

This is true even if the findings of the examination suggest the accused did not commit the crime in question.

The reason for the rule is that this type of evidence is not 100% reliable.

6. How does a polygraph test work?

A polygraph test is normally conducted in a room with only the examiner and defendant present.

The test typically begins with the examiner asking the accused questions while he/she is not connected to the polygraph machine.

The examiner then connects the machine and asks additional questions.

As the questions are answered, the machine records physiological changes in the accused. These include changes in the person's:

  • breathing rate,
  • pulse,
  • blood pressure, and
  • perspiration.

The examiner analyzes these changes as questions get answered. The idea behind these tests is that:

  • a person telling the truth will not exhibit changes in the above conditions (e.g., pulse), but
  • a person lying will show changes.

For example, signs that a person is lying may include:

  1. a change in his/her breathing rate just before a question and during an answer, or
  2. a rise in blood pressure as a question gets answered.

Note that a polygraph test does not measure whether a person is lying. Rather, it measures the signs that suggest that a person is lying.

7. How much does a private polygraph test cost?

Trained polygraph examiners administer lie detector tests for a fee.

The typical cost is between $200 and $2,000.

The specific cost usually increases with the length of the test. This means an all-day test will be on the high end of the cost range.

A typical two-hour exam is generally $200-$800.

For additional help...

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For additional guidance or to discuss your case with a criminal defense attorney, we invite you to contact us at Shouse Law Group.


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