“And the Truth Shall Set You Free” – Criminal Defense and Polygraphs

By April 3, 2009Criminal Defense

By Staff Attorney
The Gasper Law Group

Question: “If I take a polygraph, is it admissible in Court?”

Short Answer: “No”

Long Answer: “It depends on the definition of ‘it’…….Really, I’m serious”

To correctly answer your question, I’ll make a few clarifications up front. First, we’re only discussing Colorado here, not other states, or the federal system. Secondly, unless noted, we’re discussing its use in criminal cases, not civil or divorce cases. Thirdly, this is not a dissertation on whether an employer, or the military, can require you to take one as a condition of getting or keeping a particular job or security clearance.

In a pending criminal case, or an open investigation, you cannot be required to take a polygraph. It is strictly voluntary. Most importantly, it is critical to distinguish the results of the exam (i.e. did the person pass or fail) from what was actually said to the operator during the exam. So here goes.

Polygraphs have been around in one form or another for a long time. Essentially, the test measures various physiological responses to certain key questions. Generally, this would include blood pressure, pulse rate, respiration rate, and skin conductivity, all of which can show slight deviations from “normal” if a person is under stress from lying directly to the operator. In theory, these indicators are distinguishable from the obvious overall stress the subject is already under as a result of being hooked up to the instrument in the first place.
The entire process will take at least a couple of hours. You’ll first give a narrative of your side of the story and then be given instructions on how to respond. You’ll be given certain control questions (“Have you ever told a lie?”–the correct answer is ‘yes’ to that one, unless you’re perfect) to compare your responses to the two or three ultimate, key questions you’ll be asked and tested on. It’s likely to be videotaped. While the instrumentation and techniques have changed with the times, ultimately there will be a conclusion by the operator that the person was deceptive to one or more of the key questions, or was truthful. Sometimes, the results come back as inconclusive, which means even the operator does not have an opinion.
The courts have concluded that the process is not sufficiently reliable to admit the results in a criminal court proceeding. If you took one and failed, the District Attorney cannot refer to that fact in any fashion in your trial. Nor can he mention that you refused to take one, or even use the word “polygraph” at all. This cuts both ways, however. If you took one and passed, you cannot tell the jury either (unless for some reason the DA and judge agree to let you–good luck with that). Nor can you tell the jury that you were perfectly willing to take one, but the DA and police would not even let you.

So why ever bother? It can still be an invaluable investigative tool for all concerned. In a close case, the DA might be willing to let you take one anyway, and factor in the results when deciding whether to proceed with a prosecution. To have it carry any weight with the DA (who has all the power in this situation), you’ll need to either go with a police operator, or one the DA will trust. If you pass, you might get a dismissal instead of the uncertainty of a trial, and if you fail, the results don’t come in anyway. Right? That’s where it gets tricky.


What you told that operator is admissible against you in court. He is simply introduced to the jury as a police investigator, not a polygrapher, and can tell the jury whatever you told him during the exam. If you lied during the narrative portion, and the DA has other evidence to rebut that, it’ll come back to haunt you. Also, if you fail, the operator can confront you with that fact after the test. If you “fess up” to lying, and then admit doing that robbery after all, your confession can come in, too. You’ve just strengthened the DA’s case against you.
What about other tests, such as voice stress analysis, brain wave pattern testing, or measuring the dilation of the pupil for signs of deception? The same legal principles apply, and are likely to for the foreseeable future. Please note that different rules might apply for post-conviction proceedings, especially for sex offenses. There, you can often be required to submit to periodic polygraph testing as a condition of probation or parole. Failure to do so could result in revocation proceedings against you, regardless of whether you might have otherwise passed or failed.
More complicated than you thought, isn’t it? In the right case, with the right facts, the right DA, and the right client, an experienced criminal attorney might still recommend a polygraph. One key element is total candor between attorney and client. The other is effective negotiation prior to the test, in order to maximize the potential benefit and minimize the potential harm to the client. While our firm will assist you in properly preparing to take a polygraph, we will not instruct you on how to “beat the test” by taking certain countermeasures touted by some, such as taking sedatives ahead of time or placing a tack in your shoe. Such measures are of dubious value, unethical, and likely to do more harm than good. Decline the test instead, and let your attorney assist you in making the right choices in your particular case. And that’s the truth.