Skip to content
Name: People v. Xiong
Case #: F062474
Court: CA Court of Appeal
District 5 DCA
Opinion Date: 04/30/2013

Statistical evidence of random match probabilities in a DNA cold hit case is relevant. A cab driver died as a result of a single gunshot to the center of the back of the head. An analyst took blood samples of stains at the location and analyzed them for DNA. With the samples that did not match the victim, she created a profile of 15 genetic loci, plus one gender marker; a statistically extremely rare profile. It was entered into a database and, some months later, appellant was found as a match to the DNA profile. Appellant was located and an analyst confirmed that his DNA profile matched the one created from the crime scene samples. At trial, the analyst testified that in her opinion, appellant was the unknown male and presented statistics as “random match probabilities.” The defendant, relying on People v. Nelson (2008) 43 Cal.4th 1242, argued that such statistics are irrelevant in cold hit cases and challenged the sufficiency of the evidence. Affirmed. Random match probability represents the probability of finding a match by randomly selecting one profile from a population of unrelated people and is a number derived from the “product rule.” Analyzing Nelson, the Court of Appeal concluded that both the frequency (“rarity statistic”) and the random match probability are relevant in cold hit cases. Both statistics refer to the rarity of the DNA profile in the relevant populations and they do not lose their relevance when a match is found in a database. Even if a defendant is found by searching a database, the relevant population(s) are generally the major populations in the U.S., not the database population. Use of a “database match probability” would not likely have made a difference in this case because the DNA profile was astronomically rare. The court concluded that the statistical evidence here was relevant and substantial.