State v. Hummert
| Decision Date | 11 March 1997 |
| Docket Number | No. CR-95-0100-PR,CR-95-0100-PR |
| Citation | 933 P.2d 1187,188 Ariz. 119 |
| Parties | , 238 Ariz. Adv. Rep. 25 STATE of Arizona, Appellee, v. Steven Henry HUMMERT, Appellant. |
| Court | Arizona Supreme Court |
Steven Henry Hummert (Defendant) appealed his convictions for kidnaping, sexual assault, sexual abuse, and aggravated assault. Defendant claimed the trial judge erred in admitting evidence of DNA testing. Following State v. Bible, 175 Ariz. 549, 858 P.2d 1152 (1993), cert. denied, 511 U.S. 1046, 114 S.Ct. 1578, 128 L.Ed.2d 221 (1994), the court of appeals held that experts can only testify a DNA match means the defendant cannot be excluded as the donor of the sample. State v. Hummert, 183 Ariz. 484, 905 P.2d 493 (App.1995). Furthermore, the court of appeals found that the experts' testimony about their personal experience of random matches at three loci had the effect of communicating to the jury that the DNA conclusively came from Defendant. This, the court of appeals held, was prejudicial error. Id. Therefore, the case was reversed and remanded. We accepted review pursuant to Rule 31.19 of the Arizona Rules of Criminal Procedure. We have jurisdiction under Arizona Constitution, art. VI, § 5(3).
In the early morning hours of July 16, 1989, a nineteen-year-old Tempe woman and a friend were driving home from a dance club when they noticed a red Honda CRX with gray out-of-state license plates and an emblem shaped like Texas on the rear. The Honda was traveling in a different direction and turned at an intersection. A little while later they saw the same car turning in yet a different direction at another intersection.
The woman dropped off her friend and went on to her boyfriend's home, but he was not there. Again she thought she saw the red Honda. When she arrived home at approximately 3:30 a.m., a man surprised her as she was leaving her car and forced her into a neighbor's yard at gunpoint. As he did so, she saw the same red Honda CRX and was able to remember part of the license plate number. The man then raped her. The attacker attempted to strangle the victim, and in the struggle she bit him on his forearm. During the assault, he hit her around the face and head, perhaps with the butt of his gun or against a brick planter, causing severe lacerations and loss of consciousness. When she woke up, the red Honda was gone.
The victim described the car and license to the police and family members at the hospital. Propitiously, a cousin who had visited her at the hospital stopped at a nearby McDonalds, where he saw a red Honda CRX with Texas plates and a Texas-shaped emblem on the back. Defendant, who owned the car, worked at the McDonalds as a manager. When questioned by the police, Defendant claimed to have been at a party with people from work at the time of the assault. The co-workers later told police Defendant had asked them to say he left the party at 4:00 a.m. when he actually left at approximately 2:00 a.m. Defendant also had a wound on his arm that was consistent with a bite, and a pubic hair from the crime scene was consistent with his hair. Although the victim picked two other photographs from a pretrial photographic line-up, she identified Defendant as her assailant at trial.
The FBI performed DNA tests using the Restricted Fragment Length Polymorphism (RFLP) method and found that DNA extracted from semen on the victim's underwear matched Defendant's DNA at four loci, although one match was not considered because the victim shared the same allele. 1 At trial, the judge admitted evidence of the match, the criteria for declaring a match, and opinions that Defendant was not excluded by the DNA tests. After a Frye 2 hearing, the judge found that although the process of RFLP DNA profiling had been accepted by the relevant scientific community, the methods for calculating the mathematical probability of a random match were not generally accepted. The statistical probability of a random match expresses this possibility in a mathematical percentage. In Bible, for example, the witness testified, in effect, that the probability the blood on Bible's shirt came from the victim was in a "conservative" range of 60 million to one. 175 Ariz. at 582, 858 P.2d at 1185. Instead of allowing statistics on the probability of a random match, the trial judge only permitted testimony about the uniqueness of DNA and the expert's personal experience in never finding random matches under the same circumstances. If a match is random, then the sample could have come from someone other than the person in question.
Defendant was convicted of two counts of sexual assault, kidnaping, two counts of aggravated assault, and sexual abuse, all dangerous felonies. Because Defendant had a prior felony conviction and was on probation, he was sentenced to concurrent terms of twenty-five years to life on all counts.
On appeal Defendant challenged the admissibility of the DNA evidence, among other issues. The question before the court of appeals was whether "testimony regarding the existence of a 'match' between questioned and known DNA samples [is] admissible," given Bible 's holding "that random match probability calculations are inadmissible on Frye grounds." Hummert, 183 Ariz. at 489, 905 P.2d at 497. The court held that underBible, experts can only testify that a DNA match means the defendant cannot be excluded as the donor of the sample. Because the expert witnesses testified the DNA matched at three loci, the court said this was tantamount to showing conclusively the samples came from the same person. The court found this was prejudicial error because it overstated the significance of the DNA test results, implicitly conveyed to the jury the forbidden random match statistics, and made it practically impossible for the defense to cross-examine the experts without referring to the inadmissible probability statistics. Id. In its opinion, the court cited several cases from other states holding DNA evidence and the declaration of a match inadmissible in the absence of generally accepted population frequency statistics.
We have considered the admissibility and use of DNA evidence in two cases: Bible and State v. Johnson, 186 Ariz. 329, 922 P.2d 294 (1996). The present case was tried before Bible and the appeal argued and decided after Bible but before Johnson. Both cases describe the science involved in DNA testing in some detail. In the present case we make no attempt to review the scientific process except for what may be necessary to explain our reasoning.
The use of DNA profiling and matching in forensics involves three basic steps. First, through a lengthy process of chemical treatment and "photographing" using radioactive probes and X-ray film, profiles (autorads) are created of DNA evidence samples from the crime scene and samples taken from the victim and the suspects. Second, the profiles are analyzed to determine whether any of the samples match. This is done both by sight and computer analysis, comparing whether the pictures of the DNA segments photographed are the same length. Finally, the significance of the match is articulated, usually by calculating the probability of a random match. Bible, 175 Ariz. at 577, 858 P.2d at 1180.
Applying Frye, we reviewed the admissibility of DNA statistical probability evidence calculated with the product rule 3 in Bible. We held that while the RFLP method of declaring a match is admissible, the random match mathematical calculations were inadmissable because the laboratory that had applied the product rule used a flawed database. Id. at 581, 858 P.2d at 1184. The Cellmark laboratory maintained a database of DNA samples that were used to calculate how frequently the genes profiled occurred in the general population. However, this database was flawed because it had not been shown that it was in linkage equilibrium, was broad enough to be statistically valid, or was in Hardy-Weinberg equilibrium. See Johnson, 186 Ariz. at 331-33, 922 P.2d at 296-98. The "application of the product rule [by Cellmark] and the resulting opinion of the odds against a random match were not derived by applying generally accepted scientific theory" because the database was flawed. Bible, 175 Ariz. at 586, 858 P.2d at 1189. Contrary to the court of appeals' reading, as a general matter Bible did not absolutely reject the use of statistics calculating the probability of a random match. Arguably, with a database that meets Frye requirements, the product rule may be accepted as effective for calculating the probability of a random match. Id. at 590, 858 P.2d at 1193; see also Johnson, 186 Ariz. at 335, 922 P.2d at 300.
The court of appeals stated:
An autorad match is meaningless without the statistical evidence to validate the match. If the autorad reflects only sites on the DNA that are common to all human beings (monomorphic sites), the evidence obtained cannot be the basis for identifying the defendant. Thus, the expert must also show that the alleles detected by the particular probes used are polymorphic.
Hummert, 183 Ariz. at 484, 905 P.2d at 497. The purpose of the statistical interpretation of the match, however, is not to determine whether the loci measured in the autorad were poly- or mono-morphic. Because 99.9 percent of all human DNA is monomorphic--common to all people--the RFLP test has been developed to look at and measure only those areas that are polymorphic--i.e., known to vary widely from person to person. Statistical comparisons to the database are required to determine how...
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