Chapter 5:

DNA IN THE COURTROOM

The Nature of Evidence

Evidence is any statement or material object from which reasonable conclusions can be drawn. It is a broad category embracing anything perceptible to the five senses including documents, exhibits, facts agreed to by both sides, and the testimony of witnesses. Evidence in a criminal trial concerns the intent, motive, means, and opportunity to commit a crime.

In general, evidence is divided into two categories: circumstantial and physical. Circumstantial evidence consists of information gleaned from witnesses and documents that point to an individual as the perpetrator of a crime. Physical evidence consists of actual objects Ħ bodies, weapons, body fluid stains, fingerprints, hairs, fibers, etc. Ħ that are associated with the crime and may be linked to the perpetrator.

It is the work of forensic scientists to examine the physical evidence, and using the methods of science, to reconstruct the events that constituted the crime. The prosecutor must then combine this data with statements of witnesses and evidence from documents such as correspondence, telephone records and credit card receipts to develop an overall theory of the case which can be presented in court.

Scientific evidence is an increasingly important part of both civil and criminal trials. Forensic science is a growth industry. New technologies for analyzing physical evidence are growing rapidly and private companies are becoming an increasingly important resource for the legal system. The testimony of experts is the primary means of introducing scientific evidence. Because these experts are imparting information "beyond the ken" of the layperson, they must present information that goes beyond first hand observation, opinions and hearsay not permitted under ordinary rules of evidence. Lay witnesses are constrained to testify only about matters they have directly observed. Expert witnesses are allowed to draw inferences from facts which the judge or jury is not competent to draw. They may also rely on seminars, publications, records and conversations with other experts that are part of their normal course of business.

Discovery

Despite fictional presentations to the contrary (Perry Mason is a prime example), there are very few surprises in actual trials. This is because of the process called discovery, whereby opposing attorneys are permitted to learn the facts and expert opinions upon which the other side is basing its case prior to the actual trial. In addition, each side is required to provide the other side with a list of its witnesses before the start of trial.

Providing discovery materials in criminal cases is binding only upon the prosecution in all but a few states and Canada. Access to materials through the discovery process is the main avenue the defense has for learning what evidence will be presented against the accused at trial. This allows the defense to re-examine the evidence and develop alternative hypotheses to the prosecutor's case.

In California, the defense's access to scientific evidence is defined in the Griffin decision which provides that the defense can have the evidence only after the prosecution has completed their testing. Also, under both Griffin and a U.S. Supreme Court decision in Arizona v. Youngblood, the prosecution may consume the evidence in the testing process, as long as they act in good faith.

Beginning in 1989, furious battles erupted over discovery efforts in the DNA war. Gen-erally the defense has been able to examine autoradiographs from the case in question, laboratory reports, and the lab notes that support them in addition to the lab procedure manuals and proficiency testing results. Requests for additional materials such as other autoradiographs, validation studies, population data bases, and raw data face harsher scrutiny and often were not honored. Early DNA cases were marked by long and costly litigation over discovery. The defense claims that the prosecution and the labs they employ "stonewall' discovery requests. The lab resist discovery, maintaining that the requested materials are privileged, constitute trade secrets, are legally irrelevant.

Forensic labs also claim that the defense regularly makes overly burdensome and duplicitous requests for reams of material. If they were required to comply, lab personnel would be doing little else than identifying and duplicating discovery materials. DNA discovery battles are still being strenuously fought. Indeed, O.J. Simpson's chief lawyer, Robert Shapiro, has labeled Cellmark a "discovery outlaw." However most commentators would agree that many of the issues surrounding discovery already have been litigated or settled in other ways.

Scientific Evidence Admissibility Standards

The key element in whether scientific evidence is admissible is whether it is trustworthy. To be considered trustworthy, it must demonstrate accuracy (validity) and consistency (reliability). Admissibility is determined by the Frye rule, which stresses "general acceptance" or by the Federal Rules of Evidence (followed by some state courts) which stress helpfulness, reliability, and relevance.

In all of the trials to date in which DNA evidence has been involved, courts have ruled it as evidence or, on appeal, have remanded the case to the trial court in 22 reported cases and have limited its admissibility in 16 cases, generally because of statistical questions.

The Frye Standard

In the 1923 decision United States v. Frye, a District of Columbia circuit court ruled against the admissibility of lie detector evidence in a murder case because the technology had not been accepted in the relevant scientific community. Since then, most state courts have followed this general standard on whether or not to allow novel scientific evidence. The so-called Frye hearing gives the prosecution and defense the opportunity to attack adverse scientific evidence and try to keep it out of the trial. The key paragraph in this decision reads:

Just when a scientific principle or discovery crosses the line between experimental and demonstratable stages is difficult to define. Somewhere in the 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 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.

Determining "general acceptance" according to the Frye standard is a two-step procedure: (1) identifying the particular field(s) into which the scientific principle or discovery falls and the relevant scientific community; and (2) determining whether that community accepts the technology, principle, or discovery. Both the underlying theory and the procedures used to produce results must be generally accepted by scientists in the relevant fields.

To these two criteria has been added a third in some jurisdictions. In California, the additional standard evolved from the 1976 decision in People v. Kelly which held that "the proponent of the evidence must demonstrate that correct scientific procedures were done in the particular case." This third "prong" also was accepted by the court in the 1989 landmark New York v. Castro, the first case in history of where DNA evidence was excluded. A distinction lost on some courts is that the Kelly rule only requires that correct procedures be used, not that the court must determine that these procedures were performed correctly.

Legal evidence rules generally hold that how well work is performed should not be the subject of an admissibility hearing because the quality of testing in a particular case goes to the weight of the evidence and not its admissibility. It is up to the trier of fact, the judge or the jury, to determine how much weight or consideration to give that evidence. In practice, the legal distinction between the admissibility of scientific testing and the weight that should be given that testing has become increasingly blurred in DNA evidenciary hearings.

It should be noted that, at least in California, the Frye rule does not require absolute "unanimity of views within the scientific community," which, according to the California Court of Appeals, would "demand the impossible." In People v. Guerra (restated in the Reilly case), the court ruled that, "the test is met if the use of the technique is supported by a clear majority of the members of that community." Nevertheless, some courts have interpreted "general acceptance" to mean the absence of controversy, an unrealistic standard in almost any scientific or technical area.

One result of this interpretation is that Frye hearings often last longer than many trials. The mother of all Frye hearings took place in San Diego in 1987. At issue was the methodology of pre-DNA blood typing. A personal vendetta between two experts, known as the "starch wars," exacerbated the controversy which dragged on for a full year. While courts and attorneys are often reluctant to reveal the costs of proceedings, Frye hearings are expensive.

In King County (Seattle), Washington the situation may be the worst in the country. There have been over a dozen pre-trial DNA evidentiary hearings in this jurisdiction, each requiring two to six weeks of courtroom time. Most have concerned identical technologies and laboratories. In total, these hearings are estimated to have cost the local government over $1,000,000, not counting the time that personnel such as bailiffs and guards, attorneys, experts and others have lost to more productive tasks. This might be a reasonable price to pay if the controversy had been finally settled, but at this point there is no end in sight. All costs are paid by the state in more than 90% of these cases because the defendant is indigent.

The Frye rule has been criticized for its overly conservative approach and its vulnerability to manipulation by those seeking to exclude novel scientific evidence. After the Federal Rules of Evidence were enacted, a number of jurisdictions abandoned Frye.

The Federal Standard

The Federal Rules of Evidence currently in force were promulgated by the Supreme Court and enacted by Congress in 1975. While they are applicable directly only to proceedings in federal courts, they serve as the model for evidence codes in 32 states. Despite this state recognition of federal standards, the majority of states profess to follow the Frye rule, creating evidenciary ambiguity that may not be resolved until appellate courts or legislatures address the issue.

While not explicitly repudiating the Frye rule, the Federal Rules adopt a more permissive approach. They liken the standard for scientific evidence to that for other evidence, i.e. whether the probativeness, materiality, and reliability of the evidence outweighs its tendency to mislead, prejudice, and confuse the jury. The judge has more discretion under the Federal Rules.

Rule 702, which concerns admissibility, states:

if scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.

Rule 703 requires that the facts or data presented be "of a type reasonably relied on by experts in the particular field." Rule 403 excludes evidence that would cause undue prejudice or confusion. Proponents of the Federal Rules approach to admissibility believe that taken together, these rules address all the concerns embodied in the Frye rule.

Daubert v. Merrell Dow

Critics of the Federal Rules fear that the courts may be opening themselves to "junk science" by relaxing Frye, but a landmark case heard by the Supreme Court in 1993 rejected that claim. In Daubert v. Merrell Dow Pharmaceutical, Inc., the court unanimously held that the Frye rule was incompatible with and had been superseded by the adoption of the Federal Rules. It found that "vigorous cross-examination, presentation of contrary evidence, and careful [jury] instruction are the traditional and appropriate means of attacking shaky but admissible evidence." Trial courts also could still render summary judgments and directed verdicts where there was an insufficient showing of reliability.

The effect of Daubert on states where rules mirror federal standards has yet to be felt. However, it is reasonable to assume that expert testimony on DNA will be admissible after a threshold finding that it is relevant and reliable. Defendants in these jurisdictions will have a harder time suppressing DNA evidence, although stiff challenges to its admissibility will undoubtedly continue, at least for the near future. Daubert will have little or no effect on states where Frye still prevails. Some of the states even have supreme court decisions affirming Frye. The most recent state to affirm Frye is California in the Leahy case, decided in October 1994. In these states, new high court decisions or legislation are the only means to change admissibility standards.

Legislated Admissibility

By the Fall of 1994, eleven states had statutes mandating the admissibility of DNA evidence. Maryland became the first state to do so followed by Minnesota, Louisiana, and Nevada, all in 1989. Most of the legislation contains language that DNA testing is acceptable "without antecedent expert testimony" that it is "a trustworthy and reliable method." Arguably, these laws do not cover DNA analysis methods introduced after their passage, and the defense may still challenge laboratory performance and the statistical interpretation of results. As a more sophisticated defense bar mounts increasing numbers of expensive challenges to DNA evidence, it is likely that additional state legislatures will address this issue.

Expert Witnesses

While many expert witnesses represent the best in their profession, the proliferation of expert witnesses, often considered to be "hired guns" employed to shoot holes in the other side's testimony, is a remarkable development in the criminal justice system. There is hardly any kind of case not affected by these duelling experts, but psychological, medical, and DNA testimony seems to bring out the worst of them. It is difficult not to conclude that some of these individuals are willing to stretch or ignore the facts, distort the science, and become "liars for hire." Many of these witnesses derive a substantial amount or even the bulk of their income from testifying, which should be considered in determining their credibility and weighing their testimony. One California judge bemoaned the use of such witnesses by candidly calling them the beneficiaries of "a welfare system for academics." A recent article on the ethics and responsibility of expert witnesses suggests the following criteria for qualification:

• Undergraduate and graduate degrees in the relevant field of expertise;
• Specialized training in the subject area as it relates to forensic science;
• Some training in forensics;
• Professional licenses or certifications required by professional groups in the expert's discipline;
• Evidence of experimentation, teaching, and publication within the specialty area; and
• Prior disciplinary evidence directly relevant to the issues being considered.

Other elements that help to determine an expert's qualifications include: post-graduate training, publication in peer-reviewed scientific journals, the development of accepted tests and procedures, membership or leadership in appropriate scientific societies, and, only lastly, experience as an expert witness.

Ten years ago the Califonia case People v. Brown added criteria that has proven difficult to apply, ie., that the witness "must also be ċimpartial,' that is, not so personally invested in establishing the acceptance of a technique that he might not be objective about disagreements within the relevant scientific community." Neither should a witness be so invested in denigrating a technique that he exaggerates the disagreement within the scientific community. Probably the best way of gaining the testimony of impartial witnesses is for courts, rather than litigants, to appoint and pay for expert witnesses. Such is the practice in many other countries. While it is unusual in the U.S, this procedure is within the power of state and federal courts. A notable example in a case involving DNA was United States v. Yee, where the magistrate called Eric Lander, a mathematician-turned-geneticist, as an expert witness to supplement the seventeen expert witnesses called by the prosecution and defense. It is reported that Judge Ito may call his own expert witnesses during the Simpson case Kelly-Frye hearing.

Defense Strategy

Defense witnesses mount various objections to DNA evidence. They no longer try to discredit the technology itself. Years ago, DNA typing achieved such wide acceptance and proven reliability that opponents now concentrate on two principal points of attack: (1) the quality and methodology of the laboratory work, including the lab's error rate, and (2) the statistical interpretation of data. The focus of the attacks on admissibility have changed over time. As one objection was knocked down, DNA opponents came up with another. The quality and relevancy of the arguments and of the experts is decreasing, having gone from population geneticists to bio-statisticians to statisticians from completely unrelated fields. What follows is a summary of the most frequently heard complaints about DNA typing and the responses to them that might be expected from forensic scientists. More technical objections, such as bandshifting and laboratory quality assurance, are addressed in Chapter Three.

Conflict of Interest

Prosecution and defense expert witnesses in DNA cases are arguably the most contentious and disparaging in the business. Several judges have remarked that Frye hearings over DNA can be extremely vicious. Among the charges and countercharges hurled back and forth is that the opposing witnesses should be disqualified from testifying because of a conflict of interest. To a certain extent, both sides are correct. The prosecution believes that defense witnesses in DNA hearings often have a vested interest in making sure that the subject stays controversial so that they can continue the lucrative practice of testifying. The defense often believes that a practicing forensic scientist has a built-in bias or predisposition toward the prosecution's side because of the close working relationship between crime labs and law enforcement. Indeed, criminalists often are police employees.

If the forensic scientists are leaders in their field, they may be subject to a further conflict of interest. If they have developed or invented techniques or tools, they may have a proprietary interest in advancing DNA testing. They may have financial holdings in DNA labs or may have received grant funding from public or private agencies. Certainly, a jury is entitled to know about all of these connections which should be fully disclosed. At the same time, courts acknowledge that, "simply because learned experts earn a living with their expertise should not prohibit the admissibility of their opinions," as the court ruled in a recent New Jersey case.

Integrity of Specimen

Opposing expert witnesses try to raise doubts about the way DNA evidence was gathered and tested claiming that contamination may have occurred. The usual argument is that the underlying procedures for forensic DNA testing were developed in laboratories where pure and known samples were used and retesting always was an option. While this is true, the argument doesn't mention the usual results of contamination, the ease with which it can be detected, and the safeguards that are in place in most forensic DNA labs.

In almost all cases, the results of using a specimen sufficiently contaminated to alter test results simply would be ruled inconclusive. One way a specimen might be contaminated is by genetic material from the technician performing the analysis or from the person gathering the evidence. Again, this could not possibly harm the accused as an exclusion would be the result of such mishandling. Finally, there is the possibility that some of the DNA drawn from the suspect could be accidentally mixed with DNA retrieved from the crime scene. Such an accident would yield false results, especially if PCR amplification is used. To avoid this possibility, crime labs that perform PCR do it in isolation and under stringent conditions that minimize the risk of contamination.

DNA analysis is undeniably better than other tests in analyzing mixed specimens and overcoming a variety of contaminants. Because of its structure and relative stability, DNA can be tested even after mixture with acids, bases, gasoline, oil, or bleach.

Error Rate

The newest objection, which is at the heart of the Simpson defense team's argument to exclude DNA evidence, is the testing lab's error rate. In a field as complicated as forensic science there are many sources of error, most of which will lead to an inconclusive or no result. A false positive or negative error rate is impossible to measure because these are such rare events. These are the types of errors caused by human error or fraud. It should be noted that most of these types of mix-ups or failures in the chain of custody would lead to a false negative result which would be work in the accused's favor. These also are more likely to occur before the evidence is received by the laboratory. There is no rate of these kinds of errors that is acceptable. Fortunately, an error resulting in a miscarriage of justice has yet to be demonstrated in forensic DNA casework, although it is perhaps inevitable that it will occur someday.

Errors intrinsic to the testing systems, such as the inability to precisely measure DNA restriction fragment lengths, are well compensated for by interpretation guidelines which take these kinds of errors into account. The series of quality control steps built into the process also provide an excellent assurance of the quality of individual and laboratory performance. In most cases these steps should lead to corrective action long before a catastrophic error has occurred.

Minimizing laboratory errors requires a quality control program such as the ones which already are in place on a voluntary basis in the forensic laboratories. Almost all forensic DNA laboratories participate in programs which include proficiency testing and confirm that a minimum level of performance has been achieved. External proficiency testing also provides an ongoing comparison of inter-laboratory measurement error. These programs, led by the American Society of Crime Laboratory Directors Laboratory Accreditation Board are rapidly gaining momentum.

In the forensic field, the final arbiters of quality are the courts where experts under examination and cross-examination submit their results to the scrutiny of the opposing experts and the judge and jury. This added level of scrutiny is necessary to ensure quality forensic work and includes review of casework, retesting, and observation of particular tests by opposing experts. Both sides need to have equal access to forensic expertise in the interests of fairness and justice.

Population Genetics Estimates

The most contentious debate in forensic DNA involves the use of statistics to estimate the rarity of a given DNA profile. This is to be expected because the extraordinary rarity of these profiles is what gives them their conclusiveness as evidence. The rarities of the genetic profiles depend on the number of genes examined (usually four or five, often more). The frequencies of the results of each gene are multiplied to reach a combined profile frequency or the final estimate which is presented to the court.

Critics contend that among certain ethnic sub-groups, there may be arrangements of gene frequencies that differ markedly from those found in the general population. They maintain that the population base used to give frequency statistics must be drawn from the suspect's particular gene pool, i.e., if a suspect is half Vietnamese and half French, the population database used to compute the probability ra