Can a Polygraph Be Used Against You in Texas?

If you’ve ever watched a crime drama or true crime documentary, you’ve probably seen someone hooked up to a polygraph, sweating it out while being asked a series of uncomfortable questions. However, in the real world—especially in Texas—polygraphs (or lie detector tests) are treated very differently from what Hollywood might lead you to believe.

So, can a polygraph be used against you in Texas? The short answer: not usually in court. Let’s break down how polygraphs work, what the law says about them, and what you should do if someone asks you to take one.

What Is a Polygraph?

A polygraph is a device that measures physiological responses, such as heart rate, blood pressure, respiration, and skin conductivity, while a person answers questions. The theory is that when people lie, their bodies exhibit measurable stress responses. The examiner then interprets these signs to determine whether the person is being truthful.

However, there’s a big problem: polygraphs are far from foolproof. The results are highly subjective, and many experts argue that the tests can be influenced by anxiety, fear, confusion, or even the skill of the examiner.

Are Polygraphs Admissible in Texas Courts?

In Texas, polygraph results are generally not admissible in court, whether in criminal or civil trials. The Texas Court of Criminal Appeals and most appellate courts have consistently ruled that polygraph results are too unreliable to be presented as evidence.

This means:

Prosecutors can’t introduce your polygraph results to try to prove guilt.
Defense attorneys typically can’t use favorable results to prove innocence either.
Judges generally will not allow juries to consider polygraph outcomes at trial.

Even if both sides agree to introduce polygraph results (which is rare), courts still retain discretion and are likely to exclude them because of their questionable reliability.

Can You Be Asked To Take a Polygraph?

Law enforcement can ask you to take a polygraph, but you are not required to agree. In fact, it’s often in your best interest to politely decline and consult an attorney first. Polygraphs are most commonly used during the investigation stage, not in court, and what you say during the test (even if the results are never introduced) can be used against you.

For example, if you admit something during questioning, or if the examiner claims you failed, and the police confront you based on that, it can influence the direction of the investigation—even if it wouldn’t hold up in court.

Why You Should Be Cautious

Even though polygraphs aren’t admissible in court, they can still influence how a case develops behind the scenes. Investigators may use them to put pressure on suspects or witnesses. A “failed” polygraph may make someone a person of interest, while a “passed” one could wrongly create false confidence.

That’s why it’s important to speak with a criminal defense attorney before agreeing to any polygraph test. You have the right to remain silent and the right to counsel—use them.

Polygraphs and False Confessions

Polygraph tests sometimes lead to false confessions, especially when someone is scared, sleep-deprived, or confused. Under pressure, a person might say something they think will make the test “go better”—even if it isn’t true. This can quickly become part of a criminal case file, despite the test itself being inadmissible.

Speak With a Texas Criminal Defense Attorney Today

If you’re under investigation or have been asked to take a polygraph, don’t go it alone. At Guest & Gray, we’ve helped countless Texans navigate complex criminal investigations and protect their rights at every stage. Whether it’s pre-trial strategy or trial defense, we know how to handle the pressure and the games that come with it.