James Wooley
Department of Justice, Office of the District Attorney, Northern District of Ohio

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In the prosecution of criminal cases involving DNA testing, there are two distinct times in the proceedings where the proponent of DNA evidence makes critical strategy decisions. First, there is the pre-trial case, where the proponent of the DNA evidence seeks to convince the judge that the evidence is admissible for consideration by the jury. Second, there is the trial phase, where the proponent of the evidence seeks to convince the jury that it can rely on the results of the DNA testing in drawing conclusions regarding the guilt or innocence of the accused.

For years now, proponents of DNA evidence have been successful in convincing both judges and juries to accept and rely on DNA testing, whether in the form of RFLP testing results, or PCR reverse dot blot and AMPFLP testing results, because the evidence has generally been presented in a way that facilitates a clear understanding of the power of such evidence. If the correct strategic decisions continue to be made whenever STR evidence is presented in court, proponents of this powerful evidence will experience similar successes.

There are different legal standards regarding the admissibility of scientific evidence in different jurisdictions in this country. Today, the two most common standards in place are the Daubert (1) standard and the Frye (2) test. The Daubert standard, which governs the admissibility of scientific evidence in federal courts and in an increasing number of state courts (3), focuses on the reliability of the proffered evidence. The Frye test focuses on whether the underlying scientific principles and theories are generally accepted in the relevant scientific community. The Frye test continues to be controlling in several jurisdictions (4) despite the fact that the United States Supreme Court in the Daubert decision itself overruled Frye and the general acceptance test as being "too rigid and austere."

While the Frye and Daubert tests are different, it is important to note that under either standard, the concern over admissibility is triggered only by some level of novelty or uncertainty regarding the underlying theories, principles and/or methodology of the scientific evidence in question. An admissibility concern is not created by differences in DNA testing protocols between laboratories, or by differences between the way a laboratory did DNA testing yesterday and the way it does it today, or by some question regarding the reliability of the DNA results produced in a particular case, once it is shown that the theories, principles and/or methodology employed by the DNA laboratory are scientifically sound and accepted (5). In other words, there is no admissibility issue at all, let alone a close one, once it is established that there are no new or unsettled scientific theories or principles implicated in the technique in question.

Knowing that a challenge to the admissibility of scientific evidence can succeed only if there are truly novel and unsettled principles, theories, and/or methodologies at issue, the strategy that proponents of STR testing evidence should pursue in the pre-trial phase of a case is clear: above all else, stress how there are no new or unsettled principles, theories and/or methodologies implicated in STR testing and, at the same time, resist the temptation to trumpet the ways in which STR testing may be considered the new and exciting way of doing DNA testing.

Opponents of STR evidence will likely argue that STR testing is so new that scorched-earth admissibility battles like those we survived in the late 1980's and early 1990's need be waged again. In support of this argument, opponents will likely emphasize the technical ways in which STR testing may, in fact, be different from other types of DNA testing. They will also suggest that differences between the way different labs may perform STR testing suggests a lack of standards and that this is significant. When these arguments are made, the job of the proponent is to put these allegedly significant "differences" in the proper perspective for the court. In this regard, it is important for testifying DNA analysts to emphasize that choices of extraction techniques, choices of markers, choices of silver-staining versus fluorescent detection, and the like, have nothing to do with the soundness of the underlying theories, principles and methodology implicated in STR testing.

The results of a presentation of STR evidence which does not sound like a marketing pitch for a breakthrough product will be that courts will understand that STR testing is premised on already existing DNA technology knowledge; that STR testing is simply a logical and widely accepted extension of (and improvement on) the known, as opposed to a venture into uncharted scientific waters. When courts understand that there are no new scientific theories, principles and/or methodology involved in STR testing, the admissibility hurdles will be easily cleared.

There are two basic approaches to presenting DNA evidence to juries. The first approach involves a prosecutor, through expert witness testimony, presenting a detailed explanation of the underlying scientific principles and techniques involved in DNA testing in the hopes of creating a scientifically savvy jury which will be able to appreciate the scientific basis of the test results, which results are presented to the jury hours (or even days) after the jury first was told about "A" always binding with "T". In the case of STR testing, this would involve a full explanation of the structure of the DNA molecule and the variable short tandem repeat sequences at issue, the PCR methodology, the procedures for detection and typing of the length variations, and the statistical calculations. In other words, the jury would be treated to a primer on molecular genetics, followed by a virtual STR and statistics workshop.

The second approach, the one advocated by this prosecutor for all DNA evidence, including STR testing, is to apply the "K.I.S.S. Principle". The K.I.S.S. Principle advises trial lawyers who are presenting complex evidence to juries to "Keep it Simple, Stupid". When the K.I.S.S. Principle is applied, DNA evidence is presented to the jury in about half an hour, at the conclusion of which the jury has a full appreciation of the power of DNA test results in the case. When this approach is used, the jury will know that a reliable, powerful, widely accepted scientific procedure has demonstrated that a piece of biological evidence is highly likely to have come from a suspect, and the jury will also know that the suspect's complaints regarding possible problems with the test result are without merit. The jury will not know that "A" binds to "T", but I respectfully submit that they never wanted or needed to know that anyway.

The K.I.S.S. Principle with STR evidence works this way. The prosecutor calls the DNA expert who performed the test and conducts a non-technical direct examination focusing on the experience/integrity of the expert, the basic goal of DNA testing, the widespread usage and acceptance of the DNA testing technique (note the choice of the term "DNA testing" as opposed to "STR testing" is intentional, as it is not necessary that the jury need know which particular type of the many widely accepted types of DNA testing has been employed), the test results, and the fact that the evidence can be retested by anyone who claims the results are wrong. Breaking down the half hour direct examination into separate lines of questioning, it goes something like this: 1) who are you and what is it that you do? (questions and answers to explain the basic goal of the test); 2) why are you qualified to do it? (the knowledge and experience of the expert); 3) do you and others do it a lot? (the widespread usage and acceptance of the test); 4) did you do it here and with what result? (the DNA test result showing that the suspect's DNA has the same rare characteristics which were detected in the crime scene evidence); 5) have you ever done the test when it excluded a suspect? (the integrity of the expert, who call exclusions when appropriate); 6) if someone disagrees with your result, is there a scientific way to check if you got the right answer? (the defendant has the ability to retest the evidence, if he really wants to challenge the accuracy of the test result).

The advantages of this simple approach are many. First, by not conducting long, technical direct examinations, the prosecutor has made sure that the most important part of the DNA evidence–the test result–is not obscured. More than anything else, the jury needs (and wants) to know who is the likely source of the biological evidence in question, and it makes little sense to bury this information under detailed technical information.

Second, by presenting the STR evidence in a non-technical way which focuses on the widespread acceptance of all DNA testing, the power of the results and the ability to retest, the prosecutor has made it very difficult for the defense attorney to score points by claiming that STR evidence is "too new" to be considered reliable. It will also be difficult for the defense attorney to persuasively argue that "something may have technically gone wrong with the testing procedure," an attack which has been so prevalent in DNA litigation. Most defense attorneys will decline the invitation to have the evidence retested and, instead, try to impress the jury with questions about possible technical problems with the "too new" STR testing. A defense attorney will have a tough time making clear to the jury these possible technical problems if that attorney must first attempt to explain the technical background through cross examination of the prosecution's DNA expert who will certainly resist the suggestion that STR testing is, in fact, truly novel. And even if the defense attorney succeeds in making these possible technical problems clear for the jury, the defense attorney will have even more difficulty making the jury see the importance of any of the "something might have gone wrong" problems when the defense attorney has not presented any contradictory DNA test results.

Third, the simple presentation comports more closely with the way in which lay jurors are presented with expert information they rely on in their every day life. When a juror goes to a hospital and meets a doctor who recommends a course of treatment for an ailment, the juror does not make the important decision whether to follow the doctor's advise by first spending days trying to understand all the scientific underpinnings of the advice. The juror asks whether the doctor has the experience and knowledge to render the advise, whether the advice is based on medical procedures that are widely used and well accepted as reliable, whether the advice is corroborated by other expert or non-expert information, and whether the advice is contradicted by a doctor who is more experienced, more knowledgeable, and who may have used a more well accepted diagnostic procedure which has led to the differing advice. Lawyers who take a highly technical approach to arguing DNA evidence to juries are asking lay people to assess expert information in a way that is totally foreign to most of them.

Fourth, presenting the DNA evidence in a non-technical manner will mean that this type of forensic evidence will not be singled out for special scrutiny in the minds of the jury. In most cases with DNA evidence, the prosecution will also present the results of other types of forensic science testing, including ballistics testing, serology, hair and fiber evidence, and the like. The K.I.S.S. Principle is almost always invoked in the presentation of other forensic science. Treating the DNA evidence differently creates the erroneous impression that there is more reason for the jury to be concerned about reliability of this particular type of forensic science. The fact is that DNA testing is a mature forensic science and it should be presented to the jury in the same manner as other mature forensic science evidence.

Balanced against the advantages of the K.I.S.S. approach is the idea that it is valuable to have a scientifically astute jury; one that really knows where to put its A's, T's, G's, and C's. Forgetting for the moment whether it really is valuable to have such a jury, I question whether it is even remotely realistic to believe we can ever obtain such a jury in our system. I have spent significant portions of the last few years attempting, as a lay person, to understand the scientific theories, principles, and techniques involved in DNA testing. I have been able to understand a small amount of the science involved--I mean truly understand--only by talking to experts for extended periods of time, asking them to explain things over and over again, asking them follow-up questions to what they've told me, reading and re-reading scientific publications, and then going back to the experts with even more questions. It has taken literally months of interactive study and I still place myself on the steep part of the learning curve. I accept and recognize that I may not be the best control for this type of study, but my experience makes me believe that twelve lay people cannot truly learn DNA from silently sitting in a jury box for two days (or three, or four); certainly not to a level that would enable them to intelligently question the technical conclusions of any real defense or prosecution expert in DNA testing. In other words, it is naïve to think that the only arguable benefit of the technical approach-- the creation of a scientifically expert jury--will ever materialize in our system.

If STR evidence is properly presented to judges and juries, it will be embraced like all other types of DNA testing. Unless and until the legal landscape regarding all scientific evidence changes dramatically, there are no legitimate litigation risks associated with the use of STR evidence in our courts.