TODAY! A famous forensic technique – The Polygraph!
The polygraph is used in police investigations, national security investigations, background screenings for all kinds of government employment, and in reality TV shows. It is also totally bogus. There isn’t just one theory as to why it works, there’s as many as you could imagine, because there’s no real evidence it works and no science backing up the baseline assumptions! Like the best areas of every science, when you are sure something is true, you can pick and choose from a dozen different fictional mechanisms to get you there! Also, you know you’re standing on solid theoretical ground when the technique inherently resists any kind of simulated or blind testing.
It’s gotten so bad that even professional examiners no longer call it a lie detector, but a deception test. The most honest examiners would call it a nervousness test. Does it even detect that? I don’t know. No one can say. Oh and I hope you don’t get nervous from being interrogated by someone who will perhaps order your immediate arrest after the interview! Alternatively, it’s someone who will just lie to your face, say the test proves you did it, and demand an immediate confession if you want things to go well for you in prison! That’s not coercion just FYI.
A polygraph machine consists, classically, of only three sensors. First, there is a blood pressure cuff attached to the subjects arm. Second, there are respiratory sensors strapped around the subject’s chest and abdomen. Third, there is a galvanic skin response sensor attached to some of the subject’s fingers. Certain examiners will use other sensors to try to avoid defeating the machine. A pressure sensor, which the subjects sit on, is not uncommon. This is because a classic technique to fool an examiner is to clench your anus and buttocks when answering key questions. With the pressure sensor in place an examiner would detect this technique. I don’t recall whether these are used but at least hypothetically, there are jaw or biting sensors as well to detect if you are clenching or biting your tongue/cheeks as this too can be used to beat the examiner.
Finally, all these sensors are hooked up to some sort of readout machine. Either the classic paper ones you’ve seen on TV, or more likely a laptop computer.
Note I have said that you are beating the examiner, not the machine. The sensors are accurate and are accurately recording whatever data is being transmitted. Data needs to be interpreted. Examiners are the ENTIRE technique.
Many of you will be surprised by how open the process really is. The entire polygraph system is actually a series of interviews, investigations, discussions, the actual test, more actual tests, follow up tests, and finally post-testing interviews.
Before a subject is even brought in, examiners need to conduct a thorough investigation. This will help the examiner understand the subject – his background, potential pitfalls to be avoided in the questioning, potential weak spots to probe.
Then there is a pre-test interview with the subject. The examiner will outline the entire machine, the procedure, the process, and results. He will also be asking questions about things that may render a test especially difficult or impossible. For example if the subject regularly takes beta blockers, a type of heart medication that makes heart rhythm slow and steady, a polygraph will be impossible. Alternately, the subject could be mentally or physically impaired. During this interview, the examiner and the subject will craft the questions to be asked during the test together. They will finalize all the questions to be asked and go over them. The goals of the interview are many. The interviewer will want to determine if a test is possible. The interviewer will also be trying to psych out both the innocent and the guilty. Based on what the interviewer tells the subject an innocent person might feel more at ease while a guilty person might be more agitated. Finally, the interviewer wants the subject to have already heard, and be familiar with the questions so that the response measured by the machine during the test will be, in theory, based on their deceptiveness, not their shock and surprise at the question.
Then there is the test itself. The test is actually relatively short, only 10-12 questions at a time. There might be multiple tests in a row or with days between them if more questions are necessary. In each test, only a subset of the questions have actual meaning associated with them. If you are really interested in how a polygraph works read the following paragraphs carefully, as this is unlike what you’ve seen on TV.
There are presently two popular designs of polygraph question layouts. There is the Relevant-Irrelevant Question Test and the Control Question Test. CQT is far more popular than RIT. RIT is what you’ve probably seen on TV. “Are you Mr. Smith? Are you over 21? Did you rape that girl on November, 8th?” The first two are irrelevant questions, the third one is the relevant question. In theory an innocent/non-deceptive person will not react significantly differently between relevant and irrelevant questions. A deceptive/guilty person will react at the relevant questions far more greatly than the irrelevant questions.
CQT is the mainstay of questioners these days. This exam includes irrelevant/neutral questions, control questions, and relevant/issue questions. Given that each test is only 10-12 questions long, there isn’t a lot of wiggle room. Irrelevant questions are as before – “Is today Thursday? Do I have brown hair?” Relevant questions are as before – “Did you steal $10,000 from the bank? Were you involved in the bank theft in any way?” Control questions are a new type. They are designed such that any person will probably answer them with some trepidation, as they are commonplace accusations of which everyone is guilty. For example, “Before you were 18 did you ever take anything that didn’t belong to you? Did you do anything dishonest or illegal before you were 25? Before 1999 did you ever lie to get out of trouble?” In theory, a non-deceptive/innocent person will react more strongly to the control questions than to the relevant questions. A deceptive/guilty person will react more strongly to the relevant questions than the control questions.
There are other question types which are more or less common depending on the examiner, the school they went to, and whether the polygraph conference this year said they were a good idea. You might ask a relevant question right away which you intend to throw away, as the first relevant question might make anyone react. For example “Do you intend to be truthful when I ask you questions about the rape?” You might also ask questions and direct the subject to lie. For example “Before age 25 did you ever tell a lie?” The subject is also told that if they don’t show a significant reaction to the lie, the results will be inconclusive (and the threat of arrest/incarceration is EVER present). However, the real purpose of the question is that innocent people are supposed to panic at the idea of inconclusive results whereas guilty people will only care about relevant questions. The question also serves to reinforce in the validity of the test. Finally, a simulation of lie/truth detection might be used with cards shown to the subject. The purpose is to reinforce the validity and accuracy of the technique in the subject’s mind. Examiners may or may not being outright lying to you during this final kind of testing/questioning.
Now we score the test! There are several techniques, each one as ridiculous as the last. First, we have what is called the “Global” evaluation. The examiner uses the results from the sensors as well as his personal impression of the subject demeanor and body language from the test and pre-test interview to make his determination of truthfulness. Because examiners are fundamentally police/security types, nervous blacks should watch out.
Second there is the “Numerical” evaluation. This eliminates the personal feelings the examiner has about the subject and codifies the sensor’s results into sciencey sounding numbers! Strong reactions to control questions are +3, strong reactions to relevant questions are -3, small reactions are +1 or -1 respectively. Results of at least +6 are truthful, while results of -6 or lower are deceptive. Anything in between is inconclusive. What’s a major result, what’s a minor result? Oops, guess we depend on the examiner’s objectivity. Good thing he won’t use his evaluations of the person’s demeanor or body language in making that determination!
Finally there are computer scoring methods. It’s all commercial software and I don’t know their result terms or anything. Suffice it to say, it’s automated so at least all we have is the inherent bias of the system involved.
Finally there is the post-test interview. The subject is confronted with their lies and feels compelled to confess in the face of the overwhelming evidence of their guilt.
In theory any polygraph results should be reviewed in abstract by a second or third examiner who knows nothing of the case or the previous examiners results. However, in practice this is never done so there’s no point in discussing it further.
Hoo Boy, The Controversy…
Let’s start simple and work our way to studies and statistics and such. First, polygraph proponents claim that deception causes a special physiological reaction. I guess I could just stop this section right here as that pretty much invalidates all polygraph testing right there. Just boom, basic theory of the test completely wrong, unsupported, impossible to prove, MADE UP MAYBE?! Seriously, without this theory intact, the test has no basis in reality. There is no real study which shows any link between deception and physiological changes. There just aren’t any! However, I shall continue in my evisceration of the whole process.
Error rates are unknown as examiners have basically made them up. Generally polygraph results are presumed correct unless proven otherwise. There’s almost no follow-up studies to test polygraph results, no real verification criteria when there are, and they just fudge the math how they want when doing the numbers anyways.
Polygraph proponents dismiss any laboratory testing automatically. If the tests aren’t done where there are “real” consequences, or a “real” risk then the study is invalid. Because it’s a lab setting, they aren’t using actual unprosecuted rapists, thieves, or spies so no lab test will ever be sufficient.
Statistical reviews of actual polygraphs in aggregate are done using ridiculous criterion for determining if a subject was actually guilty or lying. One study used a panel of trial attorneys to determine the “truth” to be compared against. Others used only those people who later confessed, however that has obvious sampling and selection problems as well.
What studies there are that you can draw any form of data from might show the following – Victims tend to have higher false positive rates, CQT is “more accurate,” and questioning limited to one issue is “more accurate.”
The Office of Technology Assessment did a study and found that correct determinations ranged from 17% to 100%. The DoD found that polygraphs are super awesome magical devices that are just gosh darn swell.
We haven’t even brought up the issue of countermeasures in any significant way. Taking a beta blocker won’t give you a false negative but it will give you an inconclusive. It’ll also probably be detected by the examiner as your heart rate will be crazy steady and he’ll ask you if you took any. Biting the tongue, pressing your toes against the ground, flexing your buttocks/anus all have been shown to result in false negatives (false determinations of truthfulness). However, if you just read about them on the internet you probably don’t have much hope of successfully using them. Those trained by a trained polygraph examiner had the best success rates.
The Law. Oh, Law…what are you doing…
Polygraph evidence is all over the map. It also keeps coming back! No matter how many times you kill it! In fact, the original case which set a universal standard for the admissibility of scientific evidence, Frye v US , rejected it. That was in 1923! The government administers tens of thousands of polygraphs every year, stressing their accuracy and necessity. Yet when a defendant wants to use their positive results in their defense the government doesn’t want them admitted because they are horrifically inaccurate and meaningless! GOSH WHAT A CONUNDRUM.
Before the 1970’s polygraph evidence was considered too science fictiony to be admissible. Then, starting in the early 1970’s courts started admitting polygraph evidence all over the place. A couple federal courts admitted it, a California court admitted it, some New York federal courts admitted it, the Supreme Court of Massachusetts ruled it admissible over defense objections. The major federal case was reversed. The rest weren’t appealed. So there wasn’t some big rush to get the evidence in like people thought might happen. It resulted in a ridiculous split: some courts said it was per se inadmissible, some said it was admissible by stipulation (WHICH MAKES NO SENSE YOU IDIOTS), and some said it was up to the trial judge.
Then thankfully in the 1980’s things started moving around again, generally in the right direction. The Massachusetts court reversed itself. The California legislature banned it except by stipulation. A few federal circuits that had allowed it by stipulation went back to the per se exclusion rule. And of course, in 1988 the Employee Polygraph Protection Act was passed which disallowed private employers from using the polygraph.
Then a good decision on scientific evidence came down, Daubert. That case reversed Frye, opening the door to the polygraph, but put in a strict set of scientific criteria that any piece of scientific evidence must pass.
So who lets in polygraph evidence over objections? New York, Michigan, Ohio, Idaho, and New Mexico. So watch out people!
edit: I forgot to mention that Aldrich Ames, the CIA agent who spied for Russia for a long time, never beat the polygraph. He failed every time. He just convinced people at the CIA that they were false positives. Even the most rosy evaluation of the polygraph puts the false positive rate at 10% so they just believed him. Hahahahaha!