Opinion ID: 2167035
Heading Depth: 2
Heading Rank: 3

Heading: Dr. Martin Tracey's Testimony

Text: Link claims that the trial court abused its discretion in overruling his objection to testimony regarding statistical probabilities elicited from Dr. Martin Tracey, another of the state's DNA experts. Dr. Tracey testified that if two people were picked at random, the odds are less than one in 300,000 that 1) the DNA profile of the first person would match the DNA profile of the blood found in the jar of petroleum jelly and 2) the DNA profile of the second person would match the DNA profile of the sperm found on the vaginal swabs. Link argues that this testimony did not meet the standard required by Frye v. United States, 293 F. 1013 (D.C.Cir.1923), because the method that Dr. Tracey used to arrive at those numbers is not generally accepted in the scientific community. Dr. Tracey arrived at this figure by using the product rule, which provides, that if two events are independent of each other, the probabilities of each event occurring can be multiplied, and the resulting product is the probability of both events occurring. In the present case, Dr. Tracey multiplied the odds that someone at random would match the DNA profile of the blood found in the petroleum jelly  one in 48  by the odds that someone at random would match the DNA profile of the semen found on the vaginal swabs one in 6,600  to arrive at the probability of both the profiles matching two individuals picked at random. This Court has held that the product rule is generally accepted in the scientific community, and that population frequency statistics based on the product rule are admissible. State v. Kinder, 942 S.W.2d 313, 327 (Mo. banc 1996), cert. denied, 522 U.S. 854, 118 S.Ct. 149, 139 L.Ed.2d 95 (1997). Link claims, however, that this holding only allows experts to use the product rule to testify about the probability that one sample will match that of someone picked randomly, and it does not allow the expert to testify about the joint probability of two separate samples matching two separate individuals picked at random. Although it is correct that this Court's previous holding did not specifically address joint probability, this Court recognizes that the product rule is simply a mathematical principle that applies equally well for joint probability calculations. Dr. Tracey's testimony, which was based on the product rule, was therefore admissible.