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Recent court rulings addressing the admissibility of dna evidence in the courtroom

This chapter discusses the legal implications of the committee's conclusions and recommendations. It describes the most important procedural and evidentiary rules that affect the use of forensic DNA evidence, identifies the questions of scientific fact that have been disputed in court, and reviews legal developments. If such evidence is to be useful in court, scientifically acceptable procedures must permit the reliable measurement and comparison of physical features.

Likewise, a scientific basis must exist for concluding that properly performed comparisons can distinguish possible sources. As to the latter issue—the ability to differentiate between sources—the courts have demanded a more convincing showing of the exact degree of individualization yielded by DNA tests than by any other commonly used forensic technique. Some courts have deemed it necessary for experts not only to demonstrate that DNA profiles usually vary from one person to another, but also to produce uncontroversial, quantitative estimates of how rare the identifying characteristics are within particular groups and subgroups.

Whether many other forms of identification-evidence could survive comparable demands is doubtful. Consequently, this chapter describes the implications of our conclusions about the state of scientific knowledge both for testimony about the extent to which DNA samples match and for testimony about the probabilities of such matches. Legal Standards and Procedures Whether scientific evidence is admissible in criminal cases depends on whether the evidence tends to prove or disprove a fact that, under the applicable law, might matter to the outcome of the case; whether the expert presenting the evidence is qualified; whether the information is derived from scientifically acceptable procedures; and whether the potential for unfair prejudice or time-consumption substantially outweighs the probative value of the information.

We discuss those general principles and then consider their application to DNA evidence. We also describe pretrial and trial procedures that might help courts to reach decisions on admissibility and to improve the quality and use of the scientific evidence at trial. We begin with the intertwined procedural issues that arise in connection with a defendant's request for discovery, retesting, or expert assistance.

ALLEN v. STATE

The Defendant's Right to Discovery The 1992 National Research Council NRC report stated that ''all data and laboratory records generated by analysis of DNA samples should be made freely available to all parties," and it explained that "all relevant information. Certainly, there are no strictly scientific justifications for withholding information in the discovery process, and in Chapter 3 we discussed the importance of full, written documentation of all aspects of DNA laboratory operations.

Such documentation would facilitate technical review of laboratory work, both within the laboratory and by outside experts. The rules of discovery determine the circumstances under which a defendant can compel the production of such records. Because many complex technical, scientific, and statistical issues affect the use of DNA evidence, there will be cases in which defendants will contend that without comprehensive and detailed information, they are unable to prepare for trial adequately.

Although some courts have ordered liberal discovery with regard to DNA testing, 5 other courts have taken a more restrictive approach. Expertise Experts who present and interpret the results of DNA tests must be "qualified by knowledge, skill, experience, training or education" Fed. There is no well-defined threshold of knowledge or education that a witness must exceed to qualify as an expert. Because DNA identification can involve testimony as to laboratory findings, statistical interpretation of these findings, and the underlying principles of molecular biology, expertise in several fields might be required.

An expert who is qualified to testify about laboratory techniques might not be qualified to testify about molecular biology, to estimate population frequencies, or to establish that an estimation procedure is valid. Consequently, more than one expert witness might be needed. Reasonable estimates of allele frequencies in major population groups can be obtained from standard references, and many quantitatively literate experts could use the appropriate formulas in Chapters 4 and 5 to compute the relevant profile frequencies or probabilities.

Limitations in the knowledge of a technician who applies a generally accepted statistical procedure can be explored on cross-examination, 9 and, if serious questions arise, more knowledgeable specialists can be called to address those questions. In addition to hearing testimony from experts called by the parties, a court may appoint experts to report to it, rather than to the parties.

Some issues that arise with regard to DNA testing seem particularly suitable for assistance from a neutral expert. Court-appointed experts could also provide information about the composition of databases and the scientific literature dealing with specific issues. Recent court rulings addressing the admissibility of dna evidence in the courtroom courts have appointed experts to address general questions related to DNA profiling. More controversial is whether a court should appoint its own expert instead of an expert for the defense when there are more specific disputes, such as the precise location of a band on an autoradiograph.

A court might conclude that case-specific issues are better resolved with witnesses chosen by and reporting to the parties. A court could direct experts to address particular issues in their reports or pretrial summaries of testimony. After those have been exchanged, the court could then instruct each side to identify all statements in an opposing expert's opinion that are disputed and to explain the basis for the disagreement.

Controverted issues can be further narrowed at a pretrial conference see Schwarzer 1994. Procedures such as these might, for instance, persuade statistical experts to furnish a best estimate in addition to a range of estimates so that the jury will have a better sense of the degree of disagreement between the two sides.

Even if an expert responds that not enough is known as yet to make a statistically valid estimate, the court will have obtained additional information. Having more information may aid a court in ruling on challenges to the admissibility of expert testimony and may enable it to make more effective plans for how the expert testimony should be handled at trial.

In some cases, judges have departed from the traditional order of presenting testimony to enable opposing experts to testify consecutively rather than waiting for the prosecution to conclude its case. In appropriate circumstances, courts have allowed an expert's direct testimony to be presented in written or other recorded form rather than in person. In the United States, two major standards exist for deciding whether scientific findings will be admitted into evidence: In addition, some jurisdictions have adopted special statutes that provide for the admissibility of genetic testing in general or of DNA analyses in particular in criminal or civil cases.

The general-acceptance standard was first articulated in an influential 1923 federal case, Frye v United States, 293 F. In jurisdictions that follow Frye, the proponent of the scientific evidence must establish that the underlying theory and methodology are generally accepted within the relevant portions of the scientific community.

The biological and technological principles underlying the forensic methods for characterizing DNA variations have generated little controversy in court.

DNA Evidence

The sound-methodology standard is derived from phrases in the Federal Rules of Evidence. Instead of the Frye test, the court prescribed a broader framework for deciding whether proposed testimony has sufficient scientific validity and reliability to be admitted as relevant "scientific knowledge" that would "assist the trier of fact.

The court discussed other factors that might be considered. Its nonexhaustive list includes the extent to which the theory and technology have been tested, the existence of a body of peer-reviewed studies, and the known error rates of the procedure. Before Daubert, many state and federal courts had construed their rules of evidence as not including a rigid requirement of general acceptance.

The 1992 NRC report p 137 described the "helpfulness standard" used in those jurisdictions as encompassing the following factors: Cases decided in each jurisdiction help to define the scientific community in which the degree of scientific acceptance is to be ascertained, the extent of disagreement that can be tolerated, the information that may be used to gauge the extent of consensus, and the specific factors other than general acceptance that bear on relevance and helpfulness.

Evolution of DNA Evidence for Crime Solving - A Judicial and Legislative History

The courts have examined affidavits or testimony from scientists selected by the parties, specific papers in scientific periodicals, the writings of science journalists, the body of court opinions, and other scientific and legal literature, including the 1992 NRC report. Balancing and Weight Even in jurisdictions where a DNA-identification technology meets the applicable standard of scientific acceptance or validity, the results of particular tests and the manner of their presentation can be subject to challenge.

When the dangers of unfair prejudice, time-consumption, and confusion of the issues substantially outweigh the probative value of particular evidence, the trial court should exclude the evidence.

And even when the court admits expert testimony, the scientific basis and quality of the testimony can be attacked before the trier of fact. Not all expert testimony is equally convincing, and a trier of fact may choose to give admissible evidence little weight in reaching its verdict.

  1. We cannot now accurately estimate the cost of the widespread use of DNA typing, but it can be expected to run into the tens of millions of dollars a year. Indeed, the DNA specialist in this case testified that the confirmatory testing could have been completed had the proper request been made.
  2. If such evidence is to be useful in court, scientifically acceptable procedures must permit the reliable measurement and comparison of physical features. Meanwhile, unbeknownst to anyone involved in the robbery scheme, plain clothes officers of the Montgomery County police department were present in the area as part of an undercover investigation regarding a series of recent automobile thefts.
  3. The pattern of the compounds that constitute the DNA of an individual life-form determines the development of that life-form. The court concluded that the DNA typing evidence offered by the plaintiff was clearly helpful to the jury.
  4. Juries have tended to view the statistical results of this analysis as highly incriminating, which has caused many defense attorneys to challenge the validity of the results, and many prosecuting attorneys to defend them. This was, again, it's investigative information, so it has to be further investigated to determine if there is a connection to this individual, and if then they would need the comparison done with the individual's profile to the evidence profile.

Trends in the Admissibility of DNA Evidence Application of the standards for admitting scientific evidence to the admissibility of DNA profile evidence has produced divergent results. Nevertheless, the underlying theory that DNA profiling is capable of helping to identify the source of a DNA sample was never in doubt, expert testimony for the prosecution was rarely countered, and courts readily admitted the findings of commercial laboratories.

The resulting plethora of questions about laboratory procedures and analyses initiated a second wave of cases in which various courts—including the supreme courts of Georgia, 20 Massachusetts, 21 and Minnesota 22 —excluded at least some aspects of DNA evidence.

Those cases focused less on the laboratory methods for characterizing and matching DNA and more on the statistical methods for interpreting the significance of similarities in DNA samples. Many opinions in that period lagged behind the scientific publications, which responded forcefully to early speculations and questionable analyses of the importance of departures from the assumptions of statistical independence of alleles within and among VNTR loci.

Indeed, some courts reasoned that the movement of scientific opinion was essentially irrelevant under Frye as long as respected scientists continued to oppose the statistical methods. Even more recently, with the diffusion of PCR-based methods into the forensic realm, a fourth wave of cases has arrived.

The newest cases involve attacks on the procedures for ensuring the accuracy of such analyses and questions about the quantitative interpretation of genetic typing. Again, the underlying theory is not seriously questioned, and laboratories' ability at least in principle to obtain informative results is not in dispute. As with the later VNTR profiling cases, defendants have questioned whether the protocols used for forensic work are sufficient to prevent false-positive results, and they have challenged the procedures for estimating the frequencies of the genotypes that are detected after PCR amplification.

To clarify the legal relevance of our scientific conclusions and recommendations related to typing methods and statistical issues, we turn now to a more detailed review of these issues as they have arisen in the cases and legal commentary.

July Marks the 25th Anniversary of the First Use of DNA Evidence to Convict a Killer

Typing Methods VNTR Profiling Judicial recognition of the scientific acceptance of the foundations of DNA analysis is consistent with our conclusion that the methods of DNA analysis surveyed in this report are firmly grounded in molecular biology. When VNTR profiling is done with due care, the results are highly reproducible, and comparisons at four or more loci are almost certain to exclude the innocent. To the best of our knowledge, no state or federal court has held that VNTR profiling is inadmissible on the grounds that it is not scientifically accepted or sound.

Defendants have argued that the "window" within which an examiner may declare that the electrophoretic bands of VNTRs from two samples of DNA match is too wide. As the explanation in Chapter 5 indicates, because wide windows increase the chance that a match will be declared—and at the same time increase the estimates of the frequency of a matching profile—a broad range of match windows is acceptable.

We suggested in Chapter 5 that defining these alleles with floating bins is statistically preferable to the fixed-bin approach but requires access to a computerized database. That conclusion does not imply that the use of fixed bins is scientifically unacceptable.

When fixed bins are used, a dispute sometimes arises as to the frequency of a fragment that lies near the border of two bins. In Chapter 5we noted that summing the frequencies of both bins, as recommended in the 1992 NRC report, will always give an upper bound on the allele frequency. At least one court has concluded that, within the fixed approach, this summing is "the only methodology that can be characterized as being generally accepted" United States v Porter, 1994 WL 742297 [DC Super.

As we have noted, however, taking the allele frequency from the larger bin provides a better approximation to the more accurate figure obtained from floating bins. PCR-based test-evidence, however, is being introduced in a substantial number of cases, recent court rulings addressing the admissibility of dna evidence in the courtroom and courts in each jurisdiction must decide whether this new mode of DNA typing satisfies the applicable test for admitting scientific evidence, regardless of whether RFLP-based evidence has been admitted.

They characterize the former as capable of identifying a suspect but describe PCR-based testing as "answer[ing] the question of whether a suspect can be eliminated as a donor. Furthermore, very small frequencies can be obtained by testing at additional loci. Courts have shown little inclination to exclude evidence on those grounds.

At the same time, some courts, expressing concern over the impact of DNA evidence on jurors, have grafted a procedural safeguard onto the general-acceptance standard. Starting with People v Castro, 144 Misc.

Those recommendations rest not on a judgment that current error rates are so high that test results are scientifically unacceptable, but on a desire to reduce the incidence of errors to an extremely low value. It is possible that courts will want to treat compliance with such recommendations as an aspect of admissibility to encourage laboratories to follow them.

Does the prosecution have a right to be present? How specific a request must the defendant make? Of course, the right of indigent defendants to expert assistance at state expense extends beyond the right to retest. In some circumstances, the constitution requires that indigent defendants be provided with funds to retain suitable experts.

The leading case is Ake v Oklahoma, 470 U. In Ake, the Supreme Court reversed a conviction because the trial court had refused to appoint an expert to assist the indigent defendant, who was relying on an insanity defense. But Ake was a capital case in which the defense sought the assistance of a psychiatrist, and courts have differed in their interpretation of the holding Harris 1992.

Some courts have applied Ake broadly to authorize all types of expertise; others have restricted Ake to its particular facts, focusing on the type of assistance requested and on whether the prosecution was seeking the death penalty see Harrison v State, 644 N.

Furthermore, courts differ in how much of a particularized showing of need and potential prejudice a defendant must make. Some courts have held that an expert must be provided, 49 and others have found no such need. As noted in the earlier discussion of expert witnesses, courts have been more inclined to use this procedure to investigate general scientific issues related to DNA profiling than to resolve controversies related to the particulars of the DNA testing in a given case.

However, recent court rulings addressing the admissibility of dna evidence in the courtroom rule of law clearly compels such a limitation on court-appointed experts. Returning to the implications of recognizing a defendant's right to retesting whenever feasible, difficult issues can arise as to informing the jury of the defense's failure to retest or of the results of any retesting.