Wednesday, November 17, 2004
Proof of Perpetrator’s Race Unnecessary as Foundation For Admitting DNA Evidence, Court of Appeal Rules
By DAVID WATSON, Staff Writer
Proof of the race of the perpetrator is not required as a foundation for introducing evidence of the likelihood, in various racial populations, of finding a random DNA sample matching that discovered at a crime scene, the First District Court of Appeal ruled yesterday.
The court’s Div. Three declined to follow People v. Pizarro (2003) 110 Cal.App.4th 530, a case in which the Fifth District said evidence of how frequently a DNA match could be expected to occur in samples drawn from various racial groups was irrelevant in the absence of evidence that the crime was committed by a member of that group.
Writing for herself and Justice Carol Corrigan, Justice Joann C. Parrilli conceded that Pizarro supported the appeal of William Curtis Wilson, who was convicted of first degree murder in the slaying and sexual assault of a 13-year-old Vacaville girl in 2000. An expert at Wilson’s trial testified that DNA obtained from bloodstains on the victim’s clothing matched the defendant’s, and that the same genetic profile would be expected to occur in 1 of 96 billion Caucasians, 1 of 180 billion Hispanics, and 1 of 340 billion African Americans.
“We respectfully disagree with the Pizarro court’s reasoning,” Parrilli said. “The relevant group for determining random-match probabilities is the population of possible suspects, not the perpetrator’s population....The purpose of determining profile frequencies is to assess the rarity of the matched profile in the population from which the evidence sample may have come, which is frequently a much broader population than the perpetrator’s racial group.”
In Pizarro, the Fifth District reversed the defendant’s conviction for murdering his 13-year-old half sister. DNA testing matched Pizarro’s profile to the profile derived from semen on vaginal swabs taken from the victim.
Pizarro was half Hispanic and half Caucasian. An FBI expert testified that the probability of finding another unrelated Hispanic individual with a similar profile was around 1 in 250,000, while the chances of finding a matching profile in the Caucasian population was 1 in 10 million.
Because genetic profile frequencies within the major racial groups in the United States vary, separate DNA databases are maintained for each group.
Those statistics were not relevant, the Fifth District concluded, since there was no independent evidence establishing that the crime was committed by a member of either ethnic group.
But Parrilli said the court’s reasoning was flawed.
“The population of possible suspects frequently includes a range of ‘potential perpetrators,’ whose numbers and race depend on what is known about the circumstances of the crime,” she explained. “When the perpetrator’s race is unknown, the frequencies with which the matched profile occurs in various racial groups to which the perpetrator might belong are relevant for the purpose of ascertaining the rarity of the profile.”
The Pizarro court may have been “misled,” Parrilli suggested, by a reference in a 1996 report prepared by the National Research Council on evaluating forensic DNA evidence to the dangers of using a database from the “wrong” racial group.
“[T]he report’s references to ‘wrong’ databases were based on the assumption that the race of the profiled person is known. While the race of the defendant is known, the purpose of calculating the random match probability in a criminal prosecution is to assess the rarity of the profile in other possible suspects. Absent reliable information limiting the population of possible suspects to persons of a certain race, multiple databases must be consulted for that purpose.”
Justice Stuart Pollak agreed with his colleagues that Wilson’s appeal should be rejected, but wrote separately to argue that the court was taking issue only with dicta in Pizarro and not with the holding of that case.
The Pizarro opinion, authored by Presiding Justice James A. Ardaiz, discussed the issue of “alternative approaches” to selecting a database for calculating match probability “that would be acceptable when the perpetrator’s race is unknown” only in a lengthy footnote, Pollak pointed out.
While Ardaiz’s conclusion that statistics about particular racial groups are irrelevant when the race of the perpetrator is unknown “may be correct with respect to evidence of the frequency for a single ethnicity, or even for several random ethnicities,” Pollak said, “it is not true if those ethnic groups represent the largest proportion of the population and the evidence shows that the order of magnitude is similar for other racial groups.”
“The evidence is received to show the likelihood that another individual possesses the same genetic characteristics as the DNA found at the crime scene. If the odds are infinitesimal for a sizable majority of the population, evidence of that fact has a tendency in reason to prove that the DNA came from the defendant, even if smaller segments of the population were not included in calculating those percentages and the odds are not conclusive.”
He added that at Wilson’s trial, the expert testified the likelihood of a match would have been similarly small for other racial groups.
The case is People v. Wilson, A101459.
Copyright 2004, Metropolitan News Company