Most prosecutors and criminal defense attorneys are very familiar with polygraphs. Although polygraphs are generally not considered reliable enough to be admissible in court in Texas (as discussed below), they are still used outside of court during investigations or grand jury packets. Lie detector tests based on physiological changes date back to the late 1800s and have become much more sophisticated but are still considered junk science, and for good reason. Below are three things to know about polygraphs.
#1 Do Not Take a Police Polygraph
Polygraphs are frequently used by the police in investigations. Often, before charges are filed, a police officer will contact the person under investigation and in addition to asking questions, invite the person to take a police polygraph at the police station. Officers at this stage of an investigation can be very persuasive and insist that they only want to “clear some things up” or are being generous by offering to let a suspect tell his “side” of the story. In the Greater Houston area, this is a common police tactic.
In virtually all cases, it is a bad idea to speak to the police if you are the subject of an investigation, particularly without a lawyer. Similarly, it is a terrible idea to submit to a police polygraph. Polygraphs are very subjective tests and the “result” can be manipulated by the examiner. In other words, if the police suspect you of a crime, it is highly unlikely that you will “pass” the test. After you fail, the police will insist that it is time for you to “come clean” about what really happened. From the police’s perspective, this is a great way to elicit a confession from a suspect. Do not fall for this age-old trick and do not speak to the police or submit to a police polygraph under any circumstances.
#2 Polygraphs Are Not Admissible in Court
With very limited exceptions, polygraphs are not admissible in court in Texas or Federal Courts. This means that neither the defense nor the prosecution may present polygraph evidence for any reason. As noted by a Texas court “because of their inherent unreliability and tendency to be unduly persuasive, the results of a polygraph examination are not admissible in Texas for any purpose.”
This makes sense. It is not difficult to imagine that a jury would think that a polygraph examination addressing a key issue in a trial would provide the final word on a defendant’s guilt or innocence. However, in a trial, it is the jury that is the factfinder, not the polygraph. In other words, it would be a very dangerous situation if the role of a jury was effectively replaced by an unreliable machine.
In trial, it is critical that a criminal defense attorney aggressively challenge the admission and even mention of a polygraph. Very often, prosecutors employ dirty tactics such as referencing a polygraph test or “scientific test” and somehow implying that the test was failed.
#3 Polygraphs can be a useful tool for defense attorneys
Even though a jury should never see the results of a polygraph, or even hear a mention of one, polygraphs can still be a useful tool for the defense in certain situations. The first is where a defendant is under investigation. Although it would be a terrible idea to submit to a police polygraph, a criminal defense lawyer can send a client to his own polygraph examiner, where the results can potentially be shared with the police, if they are favorable. Some police investigators and prosecutors put a certain amount of weight into the results of a polygraph, and in some situation, a polygraph could theoretically be used to make it less likely that charges would be filed against a defendant.
The second situation where polygraphs are useful to the defense is in the context of grand jury packets. In a felony case, a criminal defense attorney may present evidence to the grand jury in the hope of persuading the grand jury to not indict a case (called a “no bill”). When a case is “no billed” that typically leads to a dismissal. In the right case, a criminal defense attorney will provide a grand jury packet, usually containing a letter from the attorney, as well as supporting documentation that the criminal defense attorney thinks might persuade a grand jury.
One persuasive document to include in a grand jury packet is often the results of a polygraph examination. Unlike in a jury trial, there are effectively no limitations regarding what can be submitted in a grand jury packet. A passed polygraph on a key issue can often cause a jury to issue a “no bill” in a case.
Houston criminal defense attorney Jose Ceja is a former prosecutor who regularly files grand jury packets on behalf of his clients. He regularly works with Houston polygraph examiners and advises clients who are under investigation for a variety of criminal offenses. If you are under investigation or charged with any criminal offense anywhere in the Greater Houston Area, Ceja Law Firm is an excellent choice to protect your record and your freedom.