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108 Mich. L. Rev. First Impressions 1 (2009)

handle is hein.journals/mlro108 and id is 1 raw text is: 











    FALSE, BUT HIGHLY PERSUASIVE: HOW
 WRONG WERE THE PROBABILITY ESTIMATES
                 IN MCDANIEL V BROWN?

                            David H. Kaye t


    In McDaniel v. Brown, the Supreme Court will review the use of DNA
evidence in a 1994 trial for sexual assault and attempted murder. The Court
granted certiorari to consider two procedural issues-the standard of federal
postconviction review of a state jury verdict for sufficiency of the evidence,
and the district court's decision to allow the prisoner to supplement the re-
cord of trials, appeals, and state postconviction proceedings with a
geneticist's letter twelve years after the trial. The letter from Laurence
Mueller, a professor at the University of California at Irvine, identified two
obvious mistakes in the state's expert testimony.
    This essay clarifies the nature and extent of the errors in this evidence in
Brown. One might think that the expert's letter, the opinions of the lower
courts, and the briefs-including one from 20 Scholars of Forensic Evi-
dence-would have done this, but there is more to be said.

                           I. THE DNA MATCH

    Troy Brown was tried and convicted of a brutal rape in Carlin, Nevada,
largely based on DNA evidence. Renee Romero, a criminalist for the coun-
ty, discovered semen on the victim's bloody panties. Romero reported that
DNA from the semen matched Troy's at the locations, or loci, for six genes.
Her report estimated that the versions of the genes occur in 1 in 18,900 in
the Caucasian population, 1 in 2,460,000 in the Black population and 1 in
4,800 in the Hispanic population. Additional testing showed matches at
five VNTR loci. (Variable Number Tandem Repeats are DNA sequences
that come in many possible lengths. This makes them very discriminating,
but the typing process is laborious and no longer in common use in forensic
science.) Romero estimated the random match probability (RMP) for the
additional loci to be 1 in 3 million. This quantity is the chance that a ran-
domly selected, unrelated individual would share the loci-a URMP, for
short. A more modern computation gives a value below 1 in 150 million.

     *  Distinguished Professor and Weiss Family Scholar, Pennsylvania State University,
Dickinson School of Law. A version of this essay was presented at George Washington University's
Conference, Celebrating Forty-five Years of Statistical Activity of Professor Joseph L. Gastwirth,
August 1, 2009, Washington, D.C. I am grateful to James Crow, Edward Cheng, Mitchell Holland,
and Kit Kinports for comments and to Laurence Mueller and William Thompson for email ex-
changes.
     t  Suggested citation: David H. Kaye, Commentary, False, But Highly Persuasive: How
Wrong Were the Probability Estimates in McDaniel v. Brown?, 108 Mich. L. Rev. First Impressions
1 (2009), http://www.ichiganlawreview.org/assets/fi/108/kaye.pdf.

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