Opinion ID: 1873955
Heading Depth: 1
Heading Rank: 5

Heading: Population Frequency Statistics.

Text: Dr. McElfresh testified that in his analysis to determine whether Perry's blood matched the blood found on Wallace's clothing and front doorknob, he examined three sets of chromosome groupings. In relation to that testimony, Dr. McElfresh also testified: Q. In regard to all three of those appearing in an individual, did you perform a statistical analysis in that regard? A. Yes. And that analysis simply the probability of finding all these three things in one individual is the probability of the first times the probability of the second times the probability of the third; and that number is overall we would expect to find that pattern for all three chromosomes once in 209,100,000 times. Q. Is that what makes DNA so unique? A. Yes. That is, in effect, the measure of the uniqueness between individuals of DNA. Courts addressing the admissibility of DNA evidence have distinguished between the admission of testimony that one sample of DNA matches another sample of DNA (the kind of testimony discussed in other sections of this opinion) and the admission of testimony concerning the frequency with which a given DNA pattern might occur statistically or might occur in a given population, which we denominate DNA population frequency statistics. See, e.g., Caldwell; Castro; Schwartz; Harbold; Two Bulls. We explain presently why proper proof of DNA population frequency statistics requires additional evidence from DNA matching evidence. We use the same three-pronged test that we stated earlier for testing the admissibility of evidence of DNA population frequency statistics. Restated specifically for this purpose, the test is: I. Is there a theory, generally accepted in the scientific community, that supports the conclusion that DNA population frequency statistics, as above defined, can give reliable results? II. Are there current techniques that are capable of producing reliable results in DNA population frequency statistics, as above defined, and that are generally accepted in the scientific community? III. In this particular case, did the testing laboratory perform generally accepted scientific techniques without error in the actual performance or interpretation of the tests? (The same two inquiries required by this prong in regard to DNA matching evidence are also required for DNA population frequency statistics.) The entire foundation for Dr. McElfresh's statistical testimony was his testimony that We have a database of blood samples from all over the country and we ask the question have we ever seen bands in this position.... We have asked the question `How many people would we have to look at before we saw another person like this?' Such limited, conclusory evidence is insufficient to allow admissibility under any of the individual parts of the test stated above, much less all of it. There are both scientific/mathematical and legal reasons for distinguishing between the admissibility of DNA matching evidence and the admissibility of DNA population frequency statistics. Stated simply, the evidence necessary to show a match does not by itself indicate the frequency with which a given DNA pattern might occur statistically or might occur in a given population; to establish population frequency generally requires data on the relevant populations involved as well as data for the mathematical, statistical analysis. The legal reasons for distinguishing between the admissibility of DNA matching evidence and the admissibility of DNA population frequency statistics involve the potential impact of the population frequency testimony on the jury: DNA matching testimony may say that everyone's DNA is unique, but the impact of that testimony is not as strong as quantitatively stating that 1 in 209,100,000 people might have DNA similar to the DNA in the blood found at the scene of the killing. In Schwartz, the Minnesota Supreme Court, addressing DNA population frequency statistics, wrote: In a trilogy of cases culminating with State v. Joon Kyu Kim, 398 N.W.2d 544 (Minn.1987), we held that while expert interpretation of scientific results is not foreclosed, a limitation on the use of population frequency statistics is necessary because of the danger that such evidence will have a `potentially exaggerated impact on the trier of fact' (citations omitted). In [ State v. ] Boyd, 331 N.W.2d 480, 482 (Minn.1985), we emphasized that: [I]t is [not] necessarily wrong to inform the jury of the underlying statistical evidence but that there is a real danger that the jury will use the evidence as a measure of the probability of the defendant's guilt or innocence, and that the evidence will thereby undermine the presumption of innocence, erode the values served by the reasonable doubt standard, and dehumanize our system of justice. 331 N.W.2d at 483 (citing Tribe, Trial by Mathematics: Precision and Ritual in the Legal Process, 84 Harv.L.Rev. 1329, 1355 (1971). 447 N.W.2d at 428. We agree with Schwartz's assessment that DNA population frequency evidence creates a potentially exaggerated impact on the trier of fact. We are concerned that the testimony unduly encourages the trier of fact in its determination of whether the State has proven guilt beyond a reasonable doubt to focus solely upon a numerical conclusion and to disregard the weight of other evidence. See Harbold, 124 Ill.App.3d at 382-83, 79 Ill.Dec. at 845, 464 N.E.2d at 749. These concerns can be properly addressed in an analysis of whether the probative value of the evidence outweighs its prejudicial effect. Even if population frequency statistics are otherwise admissible under the test set out in this discussion, if the prejudicial impact of the evidence outweighs its probative value, the evidence is not admissible. Ex parte Smith, 581 So.2d 531 (Ala.1991). See also Two Bulls, at 61 (trial court should determine whether statistics used to determine the probability of someone else having the same genetic characteristics is more probative than prejudicial under [Federal] Rule [of Evidence] 403). Procedures for challenging DNA evidence. Earlier, we stated that Perry contends that the trial court erred by submitting the DNA evidence to the jury without first holding a hearing concerning its admissibility. As we explain presently, we do not hold that the trial court has necessarily erred. We do hold, however, that if the admissibility of DNA evidence is challenged, the trial court should conduct a hearing outside the presence of the jury to address the considerations raised in this opinion. That hearing can be conducted either as a preliminary hearing or when the court chooses, but it should be held outside the presence of the jury, because the admissibility of the evidence is what is challenged. This is not an unusual or unduly burdensome procedure; trial courts routinely hear motions in limine prior to the offer of evidence at trial and routinely conduct evidentiary hearings. See Two Bulls, at 60. DNA evidence is discoverable, at least by the defendant. The defendant's fair trial and due process rights, Art. I, § 6, Alabama Constitution, as well as Rule 16.1, A.R.Crim.P., clearly require that the prosecution allow the defendant access to the DNA evidence. See also Schwartz, 427-28. Discovery by the State of DNA evidence in the possession of the defendant should be conducted in accordance with Rule 16.2, A.R.Crim.P. To produce uniformly sufficient information to allow a proper, well-informed determination of the admissibility of DNA evidence and to produce uniformity in DNA evidentiary hearings, we further suggest the following guidelines, which we take substantially from Castro, 144 Misc.2d at 978-79, 545 N.Y.S.2d at 999: 1. The proponent of the DNA evidence, whether defense or prosecution, should give discovery to the adversary, which should include, upon request: (1) Copies of autorads, with the opportunity to examine the originals. (2) Copies of laboratory books. (3) Copies of quality control tests run on material utilized. (4) Copies of reports by the testing laboratory issued to the proponent. (5) A written report by the testing laboratory setting forth the method used to declare a match or non-match, with actual size measurements, and mean or average size measurement, if applicable, together with standard deviation used. (6) A statement setting forth observed contaminants, the reasons therefore, and tests performed to determine the origin and the effects thereof. (7) If the sample is degraded, a statement setting forth the tests performed and the results thereof. (8) A statement setting forth any other observed defects or laboratory errors, the reasons therefore and the effects thereof. (9) Chain of custody documents. (10) A statement by the testing lab, setting forth the method used to calculate the allele frequency in the relevant population. (11) A copy of the data pool for each loci examined. (12) A certification by the testing lab that the same rule used to declare a match was used to determine the allele frequency in the population. (Note that the discovery provisions in (10), (11), and (12) specifically address evidence of DNA population frequency statistics.) 2. The proponent shall have the burden of going forward to establish that the tests and calculations were properly conducted. Once this burden is met, the burden of proof shifts to the adversary to prove, by a preponderance of the evidence, that the tests and calculations should be suppressed or modified.