Opinion ID: 1506658
Heading Depth: 1
Heading Rank: 36

Heading: HLA DQ Alpha Test

Text: The DQ Alpha test reveals an individual's form of alleles for the human-leukocyte-antigen DQ Alpha gene. The purpose of the DQ Alpha test is to identify the genotype or the two alleles that comprise the DQ Alpha gene present in the DNA sample. That result is then compared with the DQ Alpha genotype of the suspect. If the genotypes match, then the suspect cannot be excluded as a possible donor. Genetics population databases then produce the frequency with which the suspect's genotype appears in the population. Although eight alleles have been identified at the DQ Alpha locus, only six are commonly used in forensic work. Ibid. Each of those six alleles can be distinguished by specific enzyme probes. Ibid. The six alleles for DQ Alpha are denominated as 1.1, 1.2, 1.3, 2, 3, and 4. For the DQ Alpha gene, there are twenty-one possible pair combinations or genotypes. To interpret the results, the test uses a test strip with six chemical dots. Each dot consists of a specific enzyme probe that selectively binds to one of the six DQ Alpha alleles. Because the probes, rather than the DNA, are fixed on the membrane, this is called a reverse blot. Ibid. This test strip is then immersed in a solution containing the PCR product. The alleles for DQ Alpha present in the PCR product then attach to their corresponding enzyme probe on the test strip. Where the alleles bond, the dots turn blue. Two of the six dots will turn blue to indicate which two alleles constitute an individual's genotype. If an individual is homozygous, meaning that the two DQ Alpha alleles are identical, only one dot will turn blue. The DQ Alpha test performed on defendant's blood revealed that his genotype for DQ Alpha is 4,4 or homozygous. Approximately 17% of the entire population (about one-in-six people) and 11.9% of the African American population (about one-in-eight) share that genotype. DQ Alpha tests performed on a blood stain from the box-spring fabric indicated the presence of the DQ Alpha alleles 2 and 4. Schnaps's genotype for DQ Alpha was 2,4. If the blood stain on the box spring were from a single donor, defendant could have been excluded because he does not possess the 2 allele. Schnaps, whose genotype matched the alleles, however, could not be excluded. If, however, the blood on the box spring is from a mixed sample, i.e., from more than one donor, then defendant cannot be excluded. The reason is that the 4 allele, which defendant possessed, was present in the blood stain. Based on other evidence, the prosecution established that the box-spring stain was a mixed sample. Courts in New Jersey and in other jurisdictions have admitted results of PCR technology and the DQ Alpha test as scientifically reliable. See State v. Dishon, 297 N.J. Super. 254, 277, 687 A. 2d 1074 (App.Div.), certif. denied, 149 N.J. 144, 693 A. 2d 112 (1997) (finding that testimonial hearing was unnecessary to establish the general acceptance of DQ Alpha DNA testing); State v. Williams, 252 N.J. Super. 369, 381, 599 A. 2d 960 (Law Div. 1991) (holding that overwhelming and persuasive evidence pointed to general acceptance of PCR process and DQ Alpha test); State v. Haddock, 257 Kan. 964, 897 P. 2d 152 (1995) (admitting results of DQ Alpha test as scientifically reliable); People v. Palumbo, 162 Misc. 2d 650, 618 N.Y.S. 2d 197 (Sup.Ct. 1994) (same); State v. Gentry, 125 Wash. 2d 570, 888 P. 2d 1105, cert. denied, ___ U.S. ___, 116 S.Ct. 131, 133 L.Ed. 2d 79 (1995) (same). Defendant does not contest the admissibility of the PCR/DQ Alpha test results. He objects, however, to the admissibility of the results of the polymarker test, the validity of which the dissent concedes. Post at 236, 699 A. 2d at 654. Because of defendant's objection, we briefly discuss the polymarker test.