Roger Keith Coleman was arrested in Virginia for the 1982 rape and murder of Wanda Fay McCoy.  Many people felt that he had an inadequate defense counsel and that there was convincing evidence that proved his innocence, which his court- appointed lawyers---both inexperienced---failed to introduce in court.  The state's expert claimed that two pubic hairs on the body were consistent with Coleman's and it was unlikely that they had come from anyone else, although that same expert was mistaken in his hair analysis on a different murder case.  There was also another man found guilty of rape in the same small town who allegedly had confessed to the murder while with one of his victims.

Coleman maintained his innocence and he asked for a polygraph test.  He was granted it, albeit under questionable circumstances, and the state claimed that he failed it.  On May 20, 1992, Coleman was executed.

Jim McCloskey, of Centurion Ministries in Princeton, New Jersey, was deeply involved in the Coleman case for over four years.  His non-profit organization is devoted to getting justice for convicted prisoners who are innocent and he tried hard to get the evidence reconsidered.  He reports the shocking fact that that Coleman's polygraph test was administered on the morning before he was scheduled to die.

"When they offered that," he said, "we fully recognized how insane it was giving a man a polygraph on the morning of his execution, because his biological processes would be going all over the place.  We agreed to do it because we were shooting for the moon.  We were desperate and had no other options.  They did agree to allow us to have our polygrapher present for the procedure, but they sandbagged us.  They gave us the wrong address, so we never saw the procedure."

Early that morning, Coleman was taken from his cell and driven to Richmond, Virginia, where he was put into a room by himself.  He was tired and hungry, and disconsolate about what might happen to him by nightfall.  Without giving him anything to eat, the polygraph was administered and the results analyzed.  McCloskey was told that he flunked.  "We don't know whether he really flunked or not.  We don't know what questions were asked.  We've never seen anything on the results.  If he did flunk, it wouldn't surprise me given his state of mind, but we have no idea how the test was even administered."

The problem with using a polygraph under such conditions, he adds, is that the odds are stacked heavily against the person.  "You're strapped to a machine and you know that if you pass, your life might be saved, but if you flunk or they just interpret it as if you're flunking, it's the final nail on your coffin.  If you're nervous, how can they tell the difference between fear and deception?"

Advocates of the polygraph claim accuracy rates as high as 99 percent, but critics argue that the techniques are based on questionable psychological assumptions.   In a 1981 study of six polygraph interpreters, even the most experienced of them had an error rate of 18 percent, and the least experienced made classification mistakes 55 percent of the time.  In another study that used actual criminal investigation data, the accuracy range was 63 to 76 percent.  Examiners were consistently most likely to label a truthful subject as untruthful rather than the other way around.  It seems that even if the machine can achieve a much higher accuracy rate, the results depend more heavily on the skill level of the examiner.

The problems cited most often are listed below:

1. The pressure that people often feel from the idea that polygraphs will determine the truth can elicit confessions, but among them are false confessions.  There are people who, through guilt or the desire for notoriety or some other motive, feel compelled to admit to a crime they did not commit.  (Some famous murders, like the Black Dahlia in Los Angeles in 1947, have elicited dozens of confessions, and in that case, some were from people who were not even born when she was killed.)  Thus, a confession that results in a conviction is not always about accuracy.

2. The criterion of accuracy, known as the "ground truth," is difficult to pinpoint for evaluating a polygraph's assessment of guilt.  At times a panel of judges reviews all of the evidence against which to judge the polygraph and in other cases, the results are measured against a subsequent confession or the final judicial outcome.

3. Analog studies in which some accuracy statistics are based involve mock crimes that fail to adequately include the kinds of emotional components that might occur in real situations.

4. Some deceptive subjects can pass a test by using cognitive or physiological countermeasures to avoid detection. (There is even a website that teaches people how to do this.)  People with antisocial personality disorder, for example, appear to have reduced autonomic activity and show no remorse, so they may have an easier time beating the machine.  Others have devised specific tactics that appear to have some effect.  (Many polygraph examiners claim to be aware of the techniques to control one's physiology, but a 1994 study found that 50 % of subjects trained to fool the polygraph examiner succeeded.)

5. Most polygraphers are not scientists and often receive no follow-up information on the accuracy of their readings, so they don't have sufficient feedback to self-correct.

6. Polygraphs read heightened physiological responses, such as fear, which are not always about deception.

7. The polygraph analyst will come up with a certain percent of erroneous interpretations, and some studies have shown that they tend to err by calling an honest person dishonest than the other way around.  Some critics feel that this is partly due to the fact that examiners are paid to get results and they feel pressured to come up with a guilty person.

8. Not all polygraph situations follow the etiquette of allowing a second test or a complaint filed to a panel of professionals for review of a procedure.  In the case of Roger Keith Coleman, not only was his test performed under terrible conditions (no sleep, extreme agitation, hungry, anxious), but also he was not allowed a second test and no other professional was allowed to evaluate the results.  In cases where so much is at stake, both sides ought to be allowed to administer the test so that results can be compared.