Polygraph tests, or lie detectors, measure the truthfulness of a person’s statements by tracking respiration, skin conductivity, and heart rate/blood pressure. Law enforcement agencies and attorneys often use these tests to determine whether an examinee is telling the truth or not. However, you may start to wonder – are polygraphs admissible in Pennsylvania Court?
Polygraph tests are inadmissible under the Pennsylvania Rules of Evidence because they are considered too unreliable for use in court. Polygraph results are based on factors that measure physiological responses and can give false-positive or false-negative results.
Let’s take a closer look at what polygraphs are and how they work, their admissibility in court, as well as false positive and false negative results that may occur.
What is a Polygraph Test?
A polygraph test, more commonly known as a lie detector test, uses a device to record various physiological indicators and electrical signals to determine whether an individual is telling the truth or lying.
A polygraph does not tell you if a person is lying or not; it merely shows if there is a physical response to specific questions which would indicate an individual is being untruthful.
A polygraph picks up on certain bodily changes, such as increased perspiration, a spike in pulse or blood pressure, as well as other involuntary bodily changes an individual has no control over. These changes may indicate that a person is lying.
Lie detector tests are often used on suspects or witnesses as a way to support criminal investigations or by attorneys to interrogate witnesses. Some employers also use them to determine whether an employee or a job applicant is lying or not.
However, there are doubts when it comes to the reliability and accuracy of the outcomes. While many law enforcement agencies are still using them, the courts have taken issue with these tests’ reliability.
The main problem with lie detector tests is that they record physiological indicators for lying, but these indicators can also show that an examinee is anxious, nervous, or excited. Emotions like stress or excitement don’t necessarily mean that a person is lying; they may simply show that a person is under pressure.
Since polygraphs can give false positive or false negative tests, the courts have questioned their admissibility.
How Does a Polygraph Test Work?
A polygraph tests three reactions of an individual’s body:
- Respiratory: Rubber tubes are placed over a person’s abdomen and chest area to test for irregular breathing.
- Sweat glands: Metal plates are attached to the examinee’s fingers to record sweat gland activity.
- Heart Rate/ Blood Pressure: A blood pressure cuff records a person’s cardiovascular activity.
These bodily changes are measured while an examinee is answering a set of specific, precise, and clearly formulated questions.
A needle records a person’s bodily changes. Once the test is complete, the polygraph examiner will state their findings based on the results of this test.
Lie detector tests work on the assumption that if someone lies while answering questions, the physiological responses can’t be concealed by lying.
Can You Be Forced to Take a Polygraph Test?
No, it is illegal to force someone to take a polygraph test against their will. No one can administer a lie detector test without your consent.
The Employee Polygraph Protection Act or the EPPA prohibits most private employers from using polygraphs for employees or job applicants. They can’t take any action against individuals who refuse to take this test.
The same applies to law enforcement agencies – you can’t be forced to take a lie detector test, and if you refuse to take one, your refusal can’t be used against you as evidence in court. On the other hand, if you submit to a polygraph test willingly, the evidence can be used against you.
Don’t forget that you don’t have a legal obligation to undergo a lie detector test. If you have problems involving taking this test, it is best to get in touch with a reputable criminal defense attorney for legal guidance.
Is a Polygraph Test Admissible in Pennsylvania Court?
In Pennsylvania, lie detector tests are inadmissible in court, even if both parties consent. Most judges feel that polygraph results are unreliable since they are measured based on physiological responses, like stress and anxiety. It cannot be determined with 100% accuracy whether a person is lying or telling the truth.
Physiological indicators imply one or more emotions other than guilt, and as a result, inconsistent and inconclusive responses may be provided. The defects in the device used to record the test can also cause false-positive or false-negative results. Finally, there are other ways to find more reliable and accurate evidence that will better support a prosecutor’s arguments.
False Positive and False Negative Results
Polygraphs are considered unreliable because of two types of errors that can occur – false-positives and false-negatives.
A false positive occurs when an examinee is telling the truth but is reported as being deceptive. On the other hand, a false negative occurs when a person is lying but is reported as truthful.
Some of the factors contributing to false results include anxiety, fatigue, blood pressure, and inebriants such as alcohol, tobacco, and drugs, as they can alter the pulse, increase or lower heart rate and blood pressure.
Potential solutions to limit these errors include:
- Obtaining medical information about the examinee’s physical condition.
- Assessing the person’s emotional state.
- Factual analysis of the case information.
- Using control questions to evaluate an individual’s responses.
If you would like more information or if you or a loved one need a criminal defense attorney please contact Derek Steenson today!