State v. Johnson

• Decision Date: 16 July 1996
• Docket Number: No. CR-95-0393-PR,CR-95-0393-PR
• Citation: 186 Ariz. 329,922 P.2d 294
• Parties: STATE of Arizona, Appellee, v. Robert Wayne JOHNSON, Appellant.
• Court: Arizona Supreme Court

Page 294

922 P.2d 294

186 Ariz. 329

STATE of Arizona, Appellee, v. Robert Wayne JOHNSON, Appellant.

No. CR-95-0393-PR.

Supreme Court of Arizona, In Banc.

July 16, 1996.

Grant Woods, Arizona Attorney General by Paul J. McMurdie, Galen H. Wilkes, Phoenix, for State of Arizona.

Robert F. Arentz, Phoenix, for Robert Wayne Johnson.

OPINION

FELDMAN, Chief Justice.

We granted review in this case to re-examine questions involving the admissibility of DNA profile probability statistics. The questions addressed are those left open by State v. Bible, 175 Ariz. 549, 858 P.2d 1152 (1993), our previous opinion on this subject.

FACTS AND PROCEDURAL BACKGROUND

On the morning of July 9, 1991, in Sierra Vista, Arizona, a storekeeper was surprised by an intruder as she opened her business. The intruder overpowered the woman and raped her. The woman was taken to the emergency room where Sierra Vista police interviewed her and gathered her clothing. They then returned to the crime scene and retrieved paper towels the victim had used to clean herself.

Terry Hogan, a criminalist at the Arizona Department of Public Safety (DPS) crime laboratory, found that DNA extracted from blood and semen stains on the clothes and paper towels matched the DNA of a suspect, Robert Wayne Johnson. At Johnson's jury trial on sexual assault charges, the state presented evidence of the DNA match, and Hogan testified, over objection, that the probability of such a match occurring randomly was one in 312 million. The jury evidently believed that odds of one to 312 million established guilt beyond a reasonable doubt and found Johnson guilty of one count of sexual assault, a class two felony. The trial judge imposed an aggravated term of fourteen years' imprisonment and Johnson appealed, raising several issues. The court of appeals affirmed Johnson's conviction and sentence. State v. Johnson, 183 Ariz. 623, 636, 905 P.2d 1002, 1015 (App.1995).

Johnson then petitioned this court for review, claiming that the trial judge erred in admitting Hogan's testimony about the odds of a random match between Johnson's DNA and DNA extracted from the semen stains. In light of the importance of the issue and the uncertainty of the law on the point, we granted review of Johnson's claim regarding admission of the DNA evidence. See Ariz.R.Crim.P. 31.19.

DISCUSSION

A. DNA analysis

DNA analysis involves three basic steps: 1) creating the DNA profiles of evidence samples; 2) determining whether profiles of different samples match; and 3) if samples match, articulating the significance of the match, preferably by computing the probability of a random match. State v. Bible, 175 Ariz. 549, 577, 858 P.2d 1152, 1180 (1993), cert. denied, --- U.S. ----, 114 S.Ct. 1578, 128 L.Ed.2d 221 (1994).

Hogan used restricted fragment length polymorphism (RFLP) to create the DNA profiles and determine that they matched. The scientific principles underlying RFLP, its validity, and the process for declaring a match are well-documented and unchallenged here. Accordingly, we will not add to the literature by describing the complex technology and science underlying RFLP. ¹

RFLP produces a picture or DNA profile of the suspect's blood, semen, or other specimen, which is compared to the DNA profile produced from the evidence sample. These profiles are referred to as autorads. An autorad resembles an x-ray and depicts with dark stripes or bands the presence of certain gene pairs. The particular genes represented on the autorad are called alleles.

If the two DNA profiles do not match then the suspect is positively excluded. If they do match, the evidence sample came either from the suspect or an identical twin, or the match was a complete coincidence. If there is no identical twin, as in the present case, the significance of a match can be expressed in terms of the probability that the suspect's DNA profile would occur randomly. See generally M. KRAWCZAK & J. SCHMIDTKE, DNA FINGERPRINTING 61-77 (Bios Scientific Publishers 1994). The probability can be expressed either qualitatively--"probable," "highly probable"--or mathematically, as Hogan did in this case: one in 312 million. The issue under review concerns only this third step of DNA analysis: are DNA probability statistics produced by the modified ceiling method and expressed mathematically admissible under the standard for new scientific evidence? We held in Bible that admission of such evidence calculated by the product rule was error. Bible, 175 Ariz. at 577, 858 P.2d at 1180.

B. The standard for admitting new scientific evidence

The state urges us to jettison the Frye ² test for determining when new scientific evidence is ready for the courtroom and to adopt in its place the standard articulated in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993).

Under Frye, scientific evidence based on a newly postulated theory is admissible when that theory has been generally accepted in the relevant scientific community. See Bible, 175 Ariz. at 578, 858 P.2d at 1181. In contrast, Daubert says the trial judge in each case must make a "preliminary assessment of whether the reasoning or methodology underlying the testimony is scientifically valid and of whether that reasoning or methodology properly can be applied to the facts in issue." Daubert, 509 U.S. at 592-93, 113 S.Ct. at 2796.

The Frye rule has long been followed in Arizona, both before and after adoption of the Arizona Rules of Evidence. See, e.g., State v. Velasco, 165 Ariz. 480, 486, 799 P.2d 821, 827 (1990); State ex rel. Collins v. Superior Court, 132 Ariz. 180, 195-202, 644 P.2d 1266, 1281-99 (1982); State v. Valdez, 91 Ariz. 274, 277-80, 371 P.2d 894, 896-98 (1962).

In Bible we noted that Daubert "leaves many questions unanswered" and concluded that we would continue to follow Frye, at least for the present. In doing so we stated that

notwithstanding legitimate criticism of Frye, and our desire to preserve uniformity when possible [that] ... even were we to use Daubert 's reliability/scientific validity analysis, we would still be left with the problem posed by Frye: precisely when "in [the] twilight zone the evidential force of the [scientific] principle must be recognized."

175 Ariz. at 580, 858 P.2d at 1183. We have seen nothing since and, as in Bible, find nothing in the arguments or briefs to persuade us that this case presents us with a reason to abandon Frye and follow Daubert. The federal courts have not yet had a fair opportunity to apply Daubert; thus, it is too early to properly evaluate it. We therefore conclude that for the present, and for the reasons stated in Bible, the Frye rule, which has been followed without causing significant problems since it was first adopted in 1962, remains the rule in Arizona. We turn then to apply that rule to the problem presented in this case.

C. Admissibility of probability evidence

1. State v. Bible

In Bible, we reviewed the admissibility of DNA probability evidence calculated with the product rule ³ and held that the DNA probability calculations based on Cellmark Laboratory's application of the product rule were inadmissible because,

[f]or purposes of Frye, these probability calculations are flawed in three ways: (1) they are impermissibly based on the disputed assumption of linkage equilibrium; (2) the database relied on is of disputed statistical validity; and (3) the database relied on is [concededly] not in Hardy-Weinberg equilibrium.

Id. at 585-86, 858 P.2d at 1188-89. The modified ceiling method, which was used to calculate the probabilities introduced at Johnson's trial, is inextricably linked to the product rule. Therefore, as a threshold requirement, the modified ceiling method must produce results untainted by the shortcomings articulated for the product rule in Bible.

2. Assumption of linkage equilibrium

Cellmark's application of the product rule was rejected in Bible, in part because of "the disputed assumption of linkage equilibrium." Id. Linkage equilibrium refers to the principle of independent assortment, which states that the frequency of occurrence of alleles expressing different genetic traits will be determined independently of the frequency of the occurrence of other alleles in the sample. See MONROE W. STRICKBERGER, GENETICS 104-05 (3d ed., Macmillan Publishing Co., 1985). The National Research Council (NRC), in its 1992 report, DNA Technology in Forensic Science (NRC report), ⁴ illustrates the principle thusly:

From a statistical standpoint, the situation is analogous to estimating the proportion of blond, blue-eyed, fair-skinned people in Europe by separately counting the frequencies of people with blond hair, people with blue eyes, and people with fair skin and calculating their proportions [by application of the product rule].

NRC report at 76.

Thus, by way of illustration only, linkage equilibrium assumes that whether a person inherits the allele for blue eyes is unrelated to whether that person inherits the allele for blond hair or fair skin. Of course, as the NRC report points out, these three traits tend to co-occur in Nordics. Therefore the actual frequency of these three traits occurring together (assuming each trait occurs one time in ten) is not simply a straight calculation under the product rule of .10 x .10 X .10 equals 1 in 1000. Instead, because of the co-occurrence of such observable, physical traits in certain sub-populations, the actual frequency in the total population of all three traits appearing in any one individual is probably considerably higher than 1 in 1000. Id.

This does not, however, necessarily invalidate the assumption of linkage equilibrium because the alleles chosen to create the DNA profile with the RFLP protocol are non-coding, that is, they are not responsible for producing any observable characteristic. See NRC report at 77; KRAWCZAK & SCHMIDTKE, supra, at 74; MAJ. DOUGLAS A. DRIBBEN , DNA Statistical...