U.S. v. PORTER

• Decision Date: 22 December 1992
• Docket Number: No. 91-CO-1277,91-CO-1277
• Citation: 618 A.2d 629
• Parties: UNITED STATES, Appellant, v. Kevin E. PORTER, Appellee.
• Court: D.C. Court of Appeals

618 A.2d 629

UNITED STATES, Appellant, v. Kevin E. PORTER, Appellee.

No. 91-CO-1277.

District of Columbia Court of Appeals.

Argued June 30, 1992.

Decided December 22, 1992.

Appeal from the Superior Court, District of Columbia, Henry H. Kennedy, Jr., J.

Henry K. Kopel, Asst. U.S. Atty., with whom Jay B. Stephens, U.S. Atty., and John R. Fisher, Thomas J. Tourish, Jr., Patricia A. Riley, and Wanda G. Bryant, Asst. U.S. Attys., Washington, DC, were on the briefs, for appellant.

Ronald A. Goodbread, Alexandria, VA, appointed by this court, for appellee.

David Reiser, with whom James Klein, Elizabeth G. Taylor, Rosemary Herbert, and Janet C. Hoeffel, Washington, DC, were on the briefs, for Public Defender Service, amicus curiae.

Before STEADMAN and SCHWELB, Associate Judges, and MACK, Senior Judge.

SCHWELB, Associate Judge:

This appeal presents our court for the first time with the question whether"DNA" profiling evidence is admissible to corroborate the identification of a defendant in a criminal case. Provided that, as we anticipate, certain limited questions are successfully resolved on remand, the proponents of a technology which we view as a potentially valuable tool in the search for the truth carry the day.

I THE FACTS

A grand jury indicted Kevin E. Porter on February 28, 1990, on one count of rape, D.C.Code § 22-2801 (1989), and one count of carnal knowledge. Id. The indictment was precipitated by Porter's alleged sexual assault upon the fourteen year-old sister of his girlfriend. Before trial, the prosecution filed a motion requesting the court for leave to introduce expert testimony that the deoxyribonucleic acid (DNA) extracted from semen specimens taken from the crime scene matched the DNA taken from Porter's blood. The government also sought to introduce evidence that the probability of a coincidental DNA match between two unrelated black males was no higher than one in thirty million.¹ The DNA evidence was thus intended to corroborate the complainant's expected identification of Porter as her assailant and to demonstrate that it was extremely improbable that someone other than Porter had committed the crime.

In response, Porter asked the court to exclude the proffered DNA identification evidence. He argued that the technology that the FBI had used to determine that his own DNA matched the DNA taken from the semen samples was lacking in quality control assurance and had not been generally accepted in the relevant scientific community. Porter also contended that the methodologies used by the FBI to calculate "coincidental match probabilities" likewise lacked general scientific acceptance. As a result, Porter argued, the government's proffered DNA evidence failed to meet the standard for the admissibility of novel scientific techniques set forth in the landmark case of Frye v. United States, 54 App.D.C. 46, 293 F. 1013 (1923).

Porter's case was consolidated with eleven other prosecutions in which the admissibility of DNA evidence was at issue. During the twenty-day Frye hearing which followed, the judge heard testimony from eight expert witnesses, admitted over 110 exhibits, and received over 1,300 pages of briefs. The judge later issued an order, accompanied by a 93-page opinion, in which he held that the proffered DNA identification evidence was inadmissible. United States v. Porter, 120 Daily Wash.L.Rptr. 477 (Super.Ct.D.C. 1991). The judge concluded that the FBI's method for determining that a defendant's DNA matched DNA taken from the crime scene was based on procedures generally accepted in the scientific community as reliable. He ruled, however, that the FBI's procedure for calculating coincidental match probabilities, and for arriving at the figure of one in thirty million, were not based on generally accepted techniques, and that the proffered evidence was therefore inadmissible under Frye. The judge observed that a number of studies were pending on the subject of the forensic use of DNA evidence and were expected to address issues with respect to which, as of the time of writing, there was scientific disagreement. He stated that "[i]t is after these studies and others, such as the study which is being prepared by the National Academy of Sciences [NAS] have been completed, when the court should be called upon to admit DNA evidence, not before." (Emphasis in original). Id. at 507.

In the Porter case only, the government filed a pretrial appeal pursuant to D.C.Code § 23-104(a)(1) (1989). During the pendency of the appeal, the National Research Council of the NAS issued the comprehensive and long-awaited report dealing with forensic DNA methodologies to which the judge alluded in his opinion. See COMMITTEE ON DNA TECHNOLOGY IN FORENSIC SCIENCE, NATIONALRESEARCH COUNCIL, DNA TECHNOLOGY IN FORENSIC SCIENCE (1992) [hereinafter NRC REPORT]. In response to the NRC REPORT, the parties and the Public Defender Service, as amicus curiae, filed supplemental submissions to their already imposing briefs.²

We hold, essentially for the reasons stated by the trial judge, that the FBI's procedures for determining a match pass muster under Frye. We also agree with the judge that there was no consensus within the relevant scientific community in support of the FBI's calculation that the probability of a coincidental match was no higher than one in thirty million (or, a fortiori, one in forty million). We specifically decline the government's invitation to hold that the position of one group of distinguished scientists (those favoring the government's position) is more persuasive, as a matter of molecular biology or population genetics, than the position of an apparently equally distinguished group of scholars who have reached an opposite conclusion; indeed, we view the government's position on this issue as contrary to Frye. We thus agree with the trial judge's resolution of the principal issues which he addressed.

Nevertheless, we remand the case to the trial court. We do so for two reasons. First, at least in our view, the NRC REPORT, which was not available to the trial judge, suggests that the DNA evidence should be admitted on the basis of a probability calculation for which the requisite consensus may now exist. Second, we think it important to clarify a point on which the parties have not significantly focused, but which may considerably simplify the issue before the court.

We hold that it is not necessary for the prosecution to prove, in order that DNA evidence be admitted, that there is a scientific consensus as to the precise probability of a coincidental match. So long as there is a consensus that the chances of such a match are no greater than some very small³ fraction, then the evidence is probative and should be admitted on an appropriately conservative basis. If, as the information available to us now suggests, reputable scientists would agree on some such minimal figure as the bottom limit of the possibility of a coincidental match, the evidence will be admissible under the Frye standard. On remand, however, Porter must have the opportunity to contest, if he can, the sufficiency of the government's showing that the relevant scientific consensus, as defined in this opinion, now exists.

II ALLELES, CHROMOSOMES, AND POLYMORPHISMS — THE NATURE OF DNA IDENTIFICATION EVIDENCE⁴

"The techniques of DNA typing are fruits of the revolution in molecular biology that is yielding an explosion of information about human genetics." NRC REPORT, supra, at 2. The opinion of the trial court contains a detailed exposition of the technology on which the prosecution relies in this case. Porter, 120 Daily Wash.L.Rptr. at 483-85; see also United States v. Jakobetz, 955 F.2d 786, 791-93 (2d Cir. 1992), cert. denied, ___ U.S. ___, 113 S.Ct. 104,121 L.Ed.2d 63 (1992). We attempt our own brief summary, in lay terms, of an esoteric but fascinating subject.

DNA is sometimes called the blueprint of life. It contains the chemical instructions for all of life's processes, as well as the "genetic code" that defines who we are, what we look like, and where our talents lie. With the exception of identical twins, no two people have the same DNA. The makeup of one's DNA remains constant throughout one's life. In recent years, forensic technologies have been developed for removing the DNA from human cells discovered at crime scenes and for comparing the evidentiary sample with the suspect's DNA. We must determine whether these technologies pass muster under Frye.

Embedded within the nucleus of virtually every cell of each human being's body are forty-six rod-shaped chromosomes. Half of these chromosomes are inherited from one's mother and half are inherited from one's father. Each chromosome has the shape of a twisted ladder or spiral staircase. The "banisters" of this staircase are made of phosphates and sugars, while the "steps" or "rungs" consist of "base pairs," or pairs of amino acids bound together. A single DNA molecule — itself not a very large entity — contains about three billion base pairs.

Located at specific sites, or "loci," along each chromosome are large groups of base pairs known as "alleles," or "genes." Over 99% of these genes are identical among all human beings. These genes define us as persons, rather than animals, plants, or other forms of life. They account for the many shared characteristics of all human beings. The remaining genes — known as "polymorphic" genes because they vary in form from person to person — account for our unique characteristics as individuals. Many polymorphic genes are known to have definite functions: some are responsible for the color of our hair and of our eyes, some for the shape of our body and the type of our blood. Other polymorphic genes, however, appear to have no function whatever. These "junk DNA" segments, which typically consist of varying lengths of repeating sequences of base pairs, form the basis for the DNA identification evidence at issue in ...