Opinion ID: 1801755
Heading Depth: 4
Heading Rank: 6

Heading: Blood and DNA evidence

Text: Criminalist Marianne Stam testified that she detected a small amount of sperm on both the vaginal and rectal swabs collected during the autopsy, but found no evidence of the presence of an ABO blood type or PGM subtype that was different from the victim's blood type and subtype. Therefore, she explained, she could not determine the source of the semen, and could not exclude defendant as the semen donor. Stam also testified that a tissue found in the victim's kitchen trash can was spotted with blood consistent with the victim's blood type. She stated that the spots of blood appeared to have been caused by the tissue coming in contact with a wound or a bloody nose, and were not similar to marks that would be left if someone had wiped his or her hands or a knife on the tissue. She also testified that four cigarette butts found in the apartment tested positive for the presence of an enzyme found in saliva, but only two exhibited an ABO blood type, and that type was consistent with the victim's type. DNA testing was performed by criminalists Daniel Gregonis and Martin Buoncristiani. Gregonis testified that he extracted sperm cells from the vaginal swab and performed restriction fragment-length polymorphism (RFLP) testing, but was unable to determine DNA fragment lengths. He attributed the failure to the small amount of DNA and to degradation that may take place due to the unchecked growth of bacteria in a body after death. Buoncristiani testified that he conducted polymerase chain reaction (PCR) testing on samples of sperm from the vaginal and rectal swabs, by which he examined the HLADQL locus, or region, of the DNA, which varies among individuals. He testified that the testing yielded results consistent with defendant's DNA. He also testified that the particular genotype identified through the PCR testing appears in approximately 7.9 percent of African-Americans, and in approximately 1 to 8 percent of the population comprised of African-Americans, Caucasians, and Hispanics. He confirmed that if a second individual had engaged in sexual relations with the victim, and had left an equal amount of sperm or not much less sperm, the PCR testing also would have reflected a different genotype, unless the two donors had the same genotype for the particular locus.