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December 22, 1992


Appeal from the Superior Court of the District of Columbia; (Hon. Henry H. Kennedy, Jr., Trial Judge)

Before Steadman and Schwelb, Associate Judges, and Mack, Senior Judge. Opinion for the Court by Associate Judge Schwelb. Dissenting Opinion by Senior Judge Mack.

The opinion of the court was delivered by: Schwelb

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.



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. *fn1 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 "it is after these studies and others, such as the study which is being prepared by the National Academy of Sciences 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, NATIONAL RESEARCH 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. *fn2

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 small *fn3 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.



"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. , 121 L. Ed. 2d 63, 113 S. Ct. 104 (Oct. 5, 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 this case.

The remarkable technology which has provided molecular biologists with an entree into the wonders of sub-microscopic exploration has not yet enabled them to compare every base pair in one DNA molecule with every base pair in another to determine conclusively that the two molecules are, in fact, identical. Forensic scientists, seeking to apply the new technology to identify the guilty and to vindicate the innocent, have developed a "shortcut" for making this determination. After extracting and "cutting" DNA from cells taken from the crime scene and from cells taken from the defendant, they isolate, from each sample, maternal and paternal fragments of "junk DNA" from four different loci, and measure the length of the repeating sequence in each fragment. In other words, rather than comparing every base pair in the two DNA molecules, they compare eight of the defendant's genes against the genes in the same locations on the evidentiary sample DNA to see if they are consistent with each other. This process is known as "restriction fragment length polymorphism," or, more manageably, as RFLP. It is aimed at measuring the "variable number of tandem repeats," a concept which DNA aficionados rattle off as VNTR.

Because each person has thousands of polymorphic genes, it is theoretically possible for two people to have identical genes in these four locations on their DNA molecules but to have differences -- perhaps even hundreds of differences -- in other locations. Accordingly, once it has been determined that the defendant's DNA and the DNA from the evidentiary sample share identical patterns at all four of the locations examined, scientists calculate the possibility that the match is merely a coincidence and that the two samples did not actually come from the same person.

Making that calculation is generally the role of human population geneticists. The particular system followed by the FBI and presented by the prosecution to the trial court is known as "fixed bin analysis." Scientists utilizing this process first estimate, for each of the loci which was analyzed on the defendant's DNA, the fraction of people in the defendant's broad racial or ethnic group, e.g., Caucasian, Black American, or Hispanic, with genes at that locus identical to the defendant's genes. They then perform a series of multiplications to determine the fraction of the defendant's group with identical DNA fragments at all four of the loci examined. The resulting fraction is generally an astronomically low one. *fn5



A. The Frye Test.

In this jurisdiction, the starting point of our legal inquiry must be the test enunciated in Frye:

Just when a scientific principle or discovery crosses the line between the experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone the evidential force of the principle must be recognized, and while courts will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.

54 App. D.C. at 47, 293 F.2d at 1014. Although it is now forty years since James Watson of the United states and Francis crick of Great Britain received the Nobel prize for their pioneering work on the DNA molecule, see People v. Axell, 235 Cal. App. 3d 836, 845, 1 Cal. Rptr. 2d 411, 415 (1991), review denied, Cal. 3d P.2d (1992), forensic use of DNA technologies is of comparatively recent vintage (but boundless potential). See People v. Wesley, 140 Misc. 2d 306, , 533 N.Y.S.2d 643, 644-46 (1988), (Wesley I), aff'd App. Div. , 549 N.Y.S. 2d 846, 156 A.D.2d 846, 52 CRIM. LAW RPTR. 1117 (3d Dept. 1992) (Wesley II).

The use of DNA evidence in criminal cases is at the "cutting edge" of forensic science. Wesley I, supra, 140 Misc. 2d at , 533 N.Y.S. 2d at 644. This appeal therefore presents the very kind of issue which the quoted language from Frye was designed to address.

As Judge McGowan explained for the court in United States v. Addison, 162 U.S. App. D.C. 199, 201, 498 F.2d 741, 743 (1974),

the Frye standard retards somewhat the admission of proof based on new methods of scientific investigation by requiring that they attain sufficient currency and status to gain the general acceptance of the relevant scientific community.

Some jurisdictions have therefore abandoned Frye for a more liberal approach. See, e.g. Jakobetz, supra, 955 F.2d at 794. This court, however, continues to adhere to the traditional standard. Street v. Hedgepath, 607 A.2d 1238, 1244 (D.C. 1992); Jones v. United States, 548 A.2d 35, 39-40 (D.C. 1988); Ibn-Tamas v. United States, 407 A.2d 626, 637-39 (D.C. 1979).

We agree with the government that, under Frye, the proponent of a new technology must demonstrate by a preponderance of the evidence that this technology has been generally accepted in the relevant scientific community. Yee, supra, note 4, 134 F.R.D. at 195-96; see also Jakobetz, supra, 955 F.2d at 796 (declining in DNA case, to require proof of reliability beyond a reasonable doubt); United States v. Roy, 114 Daily Wash. L. Rptr. 2481, 2489 (Super. Ct. D.C. 1986); *fn6 cf. Kelly v. State, 824 S.W.2d 568, 573 (Tex. Cr. App. 1992) (requiring proof of reliability in DNA case to be by clear and convincing evidence; Texas is a non-Frye jurisdiction, however, and general acceptance need not be demonstrated).

Given the requirement in Frye of "general acceptance," "the issue is consensus versus controversy over a particular technique, not its validity." Jones, supra, 548 A.2d at 42 (citation omitted). As we bluntly put it in Jones, the prime focus is "on counting scientists' votes, rather than verifying the soundness of a scientific Conclusion." Id.; but cf. People v. Mohit, 153 Misc. 2d 22, 579 N.Y.S.2d 990, 992 (Westchester County Ct. 1992) (counting heads rarely feasible and can be of dubious value). Courts recognize that some "scientists" will testify to almost anything; *fn7 and unanimity is not required. People v. Middleton, 54 N.Y. 2d 42, 49, 429 N.E. 2d 100, 103, 444 N.Y.S. 2d 581, 584 (1981); cf. Yee, supra, 134 F.R.D. at 166, 197, 202. Nevertheless, general acceptance is general acceptance. If "scientists significant either in number or expertise publicly oppose [a new technique] as unreliable," then that technique does not pass muster under Frye. People v. Shirley, 31 Cal. 3d 18, 56, 181 Cal. Rptr. 243, 266, 723 P.2d 1354 (1982) (en banc).

The consensus that will satisfy Frye "is that of scientists, not courts," People v. Reilly, 196 Cal. App. 3d 1127, 1135, 242 Cal. Rptr. 496, 500 (1987), for " courtroom is not a research laboratory." United States v. Brown, 557 F.2d 541, 556 (6th Cir. 1977). Accordingly, "the court may not resolve a scientific dispute between opponents and proponents of the technique, the very existence of the dispute precludes admission of the testimony." Starr v. Campos, 134 Ariz. 254, , 655 P.2d 794, 797 (1982); cf. Friend v. Friend, 609 A.2d 1137, 1139-40 (D.C. 1992) (distinguishing the existence of dispute from the merits of that dispute).

We have stated that the Frye test "begins -- and ends -- with . . . whether there is general acceptance of a particular scientific methodology, not an acceptance, beyond that, of particular study results based on that methodology." Ibn-Tamas, supra, 407 A.2d at 638. The trial Judge held, and we agree, that under the Ibn-Tamas articulation, "what must be generally accepted is forensic DNA analysis and not . . . beyond that . . . the results of that analysis in a particular case." Porter, 120 Daily Wash. L. Rptr. at 495. *fn8

The trial Judge also rejected the prosecution's tentative (and somewhat astonishing) proposal that he severely restrict the categories of scientists whose views he should consider in assessing general acceptance:

It simply is not creditable to argue, and the government does not do so with much enthusiasm, that general acceptance may be premised simply on the opinion of forensic scientists. Were it otherwise, there would have been no need for a month-long Frye hearing. There is no question but that forensic scientists accept -- no qualifier is necessary -- forensic DNA evidence and believe that the time has come for its use as powerful evidence in criminal trials. While views of forensic scientists have weight and must be considered, "members of the relevant scientific field will include those whose scientific background and training are sufficient to allow them to comprehend and understand the process and form a judgment about it." Reed v. State, 283 Md. 374, 391 A.2d 364, 368 (1978). This court holds that this formulation states the relevant scientific field.

Porter, 120 Daily Wash. L. Rptr. at 495 (footnote omitted). We agree with the Judge. See also Axell, supra, 235 Cal. App. 3d at 857, 1 Cal. Rptr. 2d at 424 ("since DNA profiling is an amalgamation of primarily two disciplines, molecular biology and population genetics . . . , it appears logical to consider its acceptance by those communities for forensic use.")

B. The Scope of Review.

Generally, the decision whether or not to admit expert testimony is addressed to the sound discretion of the trial court. Street, supra, 607 A.2d at 1244; Jones, supra, 548 A.2d at 38. Where the question of the general acceptance of a new scientific technique is raised, however, the proponent will often be asking the court to establish the law of the jurisdiction for future cases. Jones, supra, 548 A.2d at 40. This is certainly true in the present instance. Accordingly, in recognition of the fact that the formulation of the law of this jurisdiction is a quintessentially appellate function, see Griffin v. United States, 618 A.2d 114, (D.C. 1992), we engage in a broad review of the trial Judge's determination whether the forensic use of DNA technology has gained general acceptance. Jones, supra, 548 A.2d at 40. In doing so, we may consider not only expert evidence of record, but also judicial opinions in other jurisdictions, as well as pertinent legal and scientific commentaries. Id. at 41. The amount of reading which the parties and amicus have invited us to undertake has therefore been challenging to say the least.

C. Determining a Match

During the Frye hearing, Porter subjected the FBI's RFLP procedure for determining a match between his own DNA and the evidentiary sample to a "blunderbuss" attack *fn9 from a number of different directions. *fn10 He reargues most or all of his contentions to this court, often in colorful if not altogether understated rhetoric. *fn11

The trial Judge addressed each of Porter's contentions in considerable detail. He concluded that the method of DNA typing used by the FBI forensic laboratory was generally accepted in the scientific community. Porter, 120 Daily Wash. L. Rptr. at 503. He found some of the defense objections to the FBI's procedures to ...

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