For the past few months, we have been working around the clock on a double homicide that we tried this past week. The following is now part of the public record in this case: There were three defendants; at the close of the state's case one defendant received a directed verdict on all charges and my client received a directed verdict on half of his charges. We went to the jury on the remaining charges and after 10 hours the jury deadlocked. We will retry the case whenever the state is ready, which could be next month.
During the trial, one state's witness told the jury that the police had threatened him and then told him what to say. He recanted his story on more than one occasion, and recanted it at trial on the stand. Another state's witness was recorded repeatedly telling an officer that he was going to do anything they wanted him to do so long as they helped him on his drug charges. This same witness let it "slip" while testifying that he had taken a polygraph, but did not say whether he passed it or failed it. Although the jury never heard the result, it is now a matter of public record that he did in fact fail that polygraph, specifically on the testimony that he was giving to the jury.
Which raises, again, this issue of polygraphs. Although the case that we tried last week will not go up on appeal and so our appellate courts will not yet have an opportunity to look at this particular issue, South Carolina defense lawyers should be alert to this admittedly narrow issue, where one party's witness has failed a polygraph and mentions the test but not the result on the stand, and be ready to make a record when it arises. The S.C. rule, in State v. Council, 335 S.C. 1, is that polygraphs are not sufficiently reliable to be admissible in court. I agree with this rule. As I have discussed before, polygraphs are not reliable and, although prosecutors and law enforcement often say that they swear by them, they typically ignore the results unless they are favorable to them. More often than not, the polygraph is used as an interrogation tool rather than a truth-seeking tool. But, there are exceptions to every rule, and I believe that there are limited circumstances when the result of a polygraph should be admitted at trial. One example is where a witness makes the mention of a polygraph but not the test result, where the mention of the test result would be prejudicial to that witness or the party who has put up his testimony.
In a situation where a witness mentions taking a polygraph, but the jury never hears the result, the jury is going to assume that that person passed his polygraph, for two reasons: first, the prosecutor surely would not put a witness on the stand who had failed a polygraph, and second, the witness surely would not have mentioned it unless he passed it. If the court gives a curative instruction (polygraph evidence is not reliable and you are to disregard any mention of the polygraph by this witness), it will only reinforce the jury's assumptions that the witness must have passed the polygraph.
Polygraphs are never admissible in court, because there is no scientific consensus as to their reliability, but what happens when a state's witness makes the mention of a polygraph, knowing that he failed it, and the state is then allowed to benefit from it? There are two situations where this "slip" occurs. First, this comes up when an attorney attempts to elicit information that would help his side of the case, for example if a defendant passed a polygraph and he says on the stand, "You know I took a polygraph don't you?" At that point, the defendant could not be allowed to benefit from his mention of the polygraph, whether intentional or not, and the results could not be admitted.
Second, there is the less common situation where the party making the "slip" is actually prejudiced by the polygraph result. What if the defendant had failed the polygraph, and then says on the stand, "You know I took a polygraph don't you?" The results could not fairly be excluded, nor should a mistrial be granted, because either result would allow the defendant to benefit from his mention of the polygraph. If the results are excluded and the trial goes forward, the jury is deceived and assumes that the defendant passed the polygraph. If a mistrial is declared, this would allow any defendant, if the trial was going badly for them, to simply say "You know I took a polygraph," and get a mistrial. The only fair resolution for this particular situation, where the mention is made and it is prejudicial to the party, would be to allow the jury to hear the polygraph result, since the defendant opened the door and could not then be allowed to benefit from his misconduct.
The same standard should be applied where the state's witness, particularly where that witness' credibility wins or loses the trial for the state, makes such a "slip." There are many circumstances where, when a party "opens the door" to otherwise inadmissible evidence, that evidence is then fair game. This is the case when a defendant takes the stand and testifies regarding his character or his propensity to commit a certain type of crime. Ordinarily, evidence of bad character is not admissible against the defendant in a criminal case, but once the defendant opens the door, it is fair game and the prosecutor can cross examine or introduce other evidence of the defendant's bad character.
I don't think that polygraphs should be admissible in court, as a general rule. But in the limited circumstances where a party, state or defendant, puts up testimony of a witness who has failed a polygraph, and that witness mentions the polygraph, that party should not be permitted to benefit by allowing the jury to assume that the witness passed the polygraph and thereby bolstering their witness' testimony.