Opinion ID: 1242445
Heading Depth: 1
Heading Rank: 10

Heading: pcr dna

Text: As noted above, the Commonwealth submitted samples of seminal fluid deposits from the vaginal swabs and bedsheet stains for DNA printing or DNA fingerprinting analysis, employing the techniques described in Spencer I, 238 Va. at 286-89, 384 S.E.2d at 781-83. The DNA samples were too degraded in quality, however, to permit analysis by that method. A sufficient quantity of DNA was isolated from sperm cells found in the samples to permit, instead, analysis by a process known as PCR DNA amplification. The Commonwealth introduced the evidence thus obtained over the defendant's objection. Spencer assigns error to this ruling on the ground that PCR DNA amplification has not been shown to be reliable and that it was not established as being generally accepted in the scientific community. PCR is an abbreviation for polymerase chain reaction. The technique is employed to amplify small quantities of deoxyribonucleic acid (DNA), the molecule that carries genetic information unique to each individual. The process proceeds in three steps. In the first step, DNA is extracted from samples of blood, sperm, hair, or other body tissue, by the use of solvents, filtration, chemical cleaning, and separation of unwanted fractions in a centrifuge. This first stage is essentially the same as that used for the isolation of DNA in the DNA printing process. In the second stage, the small quantity of isolated DNA is added to a buffer solution containing chemical primers and an enzyme called TAQ polymerase. That solution is then placed in a heating device, controlled by a microprocessor, which cycles the solution through several successive temperature plateaus. After 30 or 40 of these cycles, the DNA will have been denatured, the primers will have annealed to the DNA, identifying a gene of interest, and that gene will have been replicated or amplified by the enzyme billions of times. The third stage is the typing of the amplified gene. Nine allele-specific probes are attached to a nylon membrane, and the amplified DNA is flooded over it. The probes are designed to recognize each of the variants of the gene of interest which, in this case, was DQ-Alpha. The probes light up in the presence of the variants for which they are specific. This genetic marker system has six traits, designated, respectively, as 1.1, 1.2, 1.3, 2, 3 and 4. These traits are combined in pairs in each individual, because one trait is received from each parent. There are, according to the expert testimony, 21 possible combinations of these traits. These pairings are called genotypes. The purpose of the typing is to identify the genotype present in the amplified DNA. As stated above, the DNA extracted from the sperm found in the victim's vagina and on the bedsheet was analyzed by the foregoing method and was found to contain the DQ-Alpha genotype 1.2 and 2. The victim's DQ-Alpha genotype was 3 and 4. Spencer's DQ-Alpha genotype was 1.2 and 2. That genotype occurs in approximately 5% of the population. A combination of that genotype with Spencer's blood antigen types and enzyme types occurs in less than 1% of the population. The Commonwealth introduced the testimony of two witnesses with respect to the reliability of PCR DNA amplification. Dr. Edward T. Blake, a forensic serologist from California, had conducted the tests and described the process. Dr. Haig Kazazian, a pediatrician and board-certified geneticist from the Johns Hopkins University School of Medicine also described the technique. Both were qualified as experts by the court, and both testified that the PCR DNA technique was scientifically reliable. The theory was conceived about ten years ago and has become one of the most widely-used technical procedures in molecular biology since 1985, being used in many diagnostic applications having life or death implications. The use of the system in forensics is relatively new, although Dr. Blake testified that he had been accepted as an expert witness, relying on PCR DNA evidence, in the courts of four other states. The testimony of Drs. Blake and Kazazian was unrefuted. We have declined to adopt the Frye test in Virginia. Spencer III, 238 Va. at 573 n. 5, 385 S.E.2d at 856 n. 5; O'Dell v. Commonwealth, 234 Va. 672, 695-97, 364 S.E.2d 491, 504, cert. denied, 488 U.S. 871, 109 S.Ct. 186, 102 L.Ed.2d 154 (1988). When scientific evidence is offered, the court must make a threshold finding of fact with respect to the reliability of the scientific method offered, unless it is of a kind so familiar and accepted as to require no foundation to establish the fundamental reliability of the system, such as fingerprint analysis, Avent v. Commonwealth, 209 Va. 474, 478, 164 S.E.2d 655, 658 (1968); or unless it is so unreliable that the considerations requiring its exclusion have ripened into rules of law, such as lie-detector tests, Robinson v. Commonwealth, 231 Va. 142, 156, 341 S.E.2d 159, 167 (1986); or unless its admission is regulated by statute, such as blood-alcohol test results, Code §§ 18.2-268(O), -268(Y). In making the threshold finding of fact, the court must usually rely on expert testimony. If there is a conflict, and the trial court's finding is supported by credible evidence, it will not be disturbed on appeal. Even where the issue of scientific reliability is disputed, if the court determines that there is a sufficient foundation to warrant admission of the evidence, the court may, in its discretion, admit the evidence with appropriate instructions to the jury to consider the disputed reliability of the evidence in determining its credibility and weight. See O'Dell, 234 Va. at 696-97, 364 S.E.2d at 505. If admissibility were conditioned upon universal acceptance of forensic evidence, no new scientific methods could ever be brought to court. Indeed, if scientific unanimity of opinion were necessary, very little scientific evidence, old or new, could be used. Wide discretion must be vested in the trial court to determine, when unfamiliar scientific evidence is offered, whether the evidence is so inherently unreliable that a lay jury must be shielded from it, or whether it is of such character that the jury may safely be left to determine credibility for itself. In the present case, the court made a finding, based upon credible and unrefuted evidence, that the PCR DNA test results were sufficiently reliable to warrant submission to the jury. We will not disturb that finding.