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DNA Evidence

Simon A. Cole

THE DOUBLE HELIX AND THE LAW OF EVIDENCE. David H. Kaye. xviii + 330 pp. Harvard University Press, 2010. $45.

GENETIC JUSTICE: DNA Data Banks, Criminal Investigations, and Civil Liberties. Sheldon Krimsky and Tania Simoncelli. xviii + 406 pp. Columbia University Press, 2011. $29.95.

Over the past 25 years, DNA profiling has developed into an enormously powerful policing technology. This development, however, has raised a number of difficult legal, political and scientific questions. These include questions regarding such matters as how broad the government’s ability to collect DNA samples should be, what sort of genetic information should be retained in government DNA databases, in what manner those databases should be searched, what degree of scientific acceptance is needed to warrant using a genetic analysis as forensic evidence, and how the results of genetic analyses should be presented to judges and jurors. These debates and others have spawned a number of new books, including The Double Helix and the Law of Evidence, by David H. Kaye, and Genetic Justice, by Sheldon Krimsky and Tania Simoncelli. Both books are valuable additions to the literature. They thoroughly cover two quite different aspects of the development of DNA profiling: The first examines the past, and the second reflects on the future.

The Double Helix and the Law of Evidence, although it touches on other issues, is primarily concerned with the disputes over the legal admissibility of DNA evidence in the United States during the early and mid-1990s. That period saw fierce courtroom battles as government and defense attorneys litigated, first, whether DNA evidence was ready to be used in court, and, second, what sorts of statements about the value of the evidence expert witnesses were justified in making. Because DNA analysis was a new technology and because, unlike many other forensic techniques, it emanated from “high science,” a number of renowned scientists, primarily molecular biologists, were mustered by both sides. As the courtroom struggles intensified, the debates between these heavyweights—scientists such as Eric Lander, Kenneth Kidd, Richard Lewontin and James Crow—bled over into scientific journals. The National Research Council (NRC) was soon drawn into the fray, convening two committees, which issued two somewhat contradictory reports in 1992 and 1996.

Author David H. Kaye is a law professor renowned for his meticulous attention to detail, careful argumentation and impressive technical mastery of statistical and scientific issues. He was also a player in the events described above: He consulted occasionally for defendants, served on the second NRC committee and published many scholarly articles commenting on the weaknesses of arguments made by courts, scientists and other legal scholars. The Double Helix and the Law of Evidence offers a detailed, authoritative accounting of the legal cases of this period and of scientific debates that ran in parallel in the pages of scientific journals.

The debates concerned a number of issues. One was the question of what constituted proper scientific controls over the interpretation of the output of analyses of genetic materials. Two questions regarding population genetics were also important: What can scientists assume about the degree of “structure” in the human population? And, is it justifiable to treat different genetic loci as independent when calculating the value of genetic evidence? Kaye offers a number of simple exercises and analogies to make this technical material accessible to lay readers.

Kaye tends to be more critical of defense attorneys and their experts than he is of the government, and occasionally he treats judicial insults of expert witnesses as statements of fact, rather than considering that they might be rhetorical ways of justifying the decisions judges want to make. But he is generally equitable in dispensing trenchant criticism, and few characters in the story (the statistical geneticist Newton Morton is one) escape completely unscathed. When Kaye inserts himself into the narrative, he strikes an appropriate balance, usually letting the reader know what he thinks about an issue without being at all self-aggrandizing.

Kaye notes at the outset that he is not a historian. This imposes more limitations than the trivial one he acknowledges—that he is not always accurate about his characters’ precise ages. One limitation is that the book lacks context. For example, although Kaye is often critical of the quality of lawyering in the cases he discusses, only once does he mention the crippling lack of resources under which most criminal defense attorneys in the United States operate. (The O. J. Simpson trial, which Kaye analyzes in depth, may, with some justification, be viewed as the exception that proves the rule.) A reader looking for a better contextualized and more readable—although less legally and technically detailed—narrative of these events might turn to Genetic Witness: Science, Law, and Controversy in the Making of DNA Profiling (2007), by historian of science Jay D. Aronson.

Lack of context is also evident in the book’s conclusion, when Kaye turns to the topic of lessons learned and discusses ways that the comprehension and use of science in legal proceedings might be improved. He focuses exclusively on the perceived biases of expert witnesses and the various mechanisms that have been proposed to mitigate those biases. Surprisingly, there is no discussion of whether biases (not to mention lack of scientific literacy) among judges might be an issue of equal, if not greater, importance. There is ample evidence in The Double Helix and the Law of Evidence that judges not only failed to understand the scientific issues well but may also have been reluctant to deprive the government of evidence that could be used to convict accused criminals. Although Kaye may view this as, in retrospect, the correct outcome, that does not necessarily mean it emanated from the right intentions.

Kaye concludes by declaring that “the great DNA wars over admissibility are over,” but he acknowledges that thorny issues remain, such as so-called low-copy-number DNA analyses. In addition, although the issues relating to population genetics have been thoroughly aired, the question of how to interpret DNA analyses, especially analyses of “mixtures,” samples that contain DNA from more than one individual, remains contentious and has received less attention from the courts, the NRC and scientific journals. Nonetheless, with the imprimatur of the courts, a public myth of the “infallibility” of DNA profiling has arisen.

Genetic Justice begins, in a sense, where Kaye’s book leaves off—with this notion of infallibility. It recounts the notorious case of the “phantom of Heilbronn,” in which German officials spent $18 million and 16,000 hours of overtime, analyzing 3,000 DNA samples taken without any direct suspicion, in the search for a supposed serial killer—a search based on a DNA profile that turned out to belong to a woman who worked at a factory packing swabs used for DNA sampling. Authors Sheldon Krimsky, a public-policy scholar well known for his work on the influence of corporate money on scientific research, and Tania Simoncelli, the former science advisor to the American Civil Liberties Union, note that it was the perceived infallibility of DNA profiling that prevented the authorities from considering alternative explanations for the results they were seeing.

In contrast to Kaye’s book, Genetic Justice addresses the myriad privacy issues raised by the expansion of DNA profiling and DNA databases. Although DNA databases were initially limited to murderers and rapists, they rapidly expanded to encompass the perpetrators of other crimes and are now becoming an essential part of law-enforcement infrastructure. This expansion has been taken to its greatest extreme in the United Kingdom, where in 2008 the national database contained the DNA profiles of 4.6 million people (7.6 percent of the population). More than one-fifth of these profiles—about a million of them—were from individuals who had not been convicted of, or even charged with, a crime, but had merely been arrested. Although the all-encompassing nature of the U.K. database was recently deemed a contravention of the European Convention on Human Rights, the United States, among other countries, appears determined to follow the United Kingdom’s example.

Genetic Justice offers a comprehensive discussion of contemporary civil-liberties intrusions associated with DNA profiling. In DNA “dragnets,” DNA samples are demanded from inhabitants of a defined geographic area fitting a certain (usually rather vague) physical description. Krimsky and Simoncelli argue that these samples are not truly voluntary, because the police use intimidation and coercion to procure them. The authors also note that these dragnets are rarely effective at solving the crime in question and that the samples are rarely destroyed at the conclusion of the investigation; instead, they are added to the local DNA database.

Familial searching is the practice of identifying suspects by searching the database for partial matches to a crime-scene sample. Inferring that individuals who match the sample at many but not all loci may be close blood relatives of the true source of the sample, the police generate suspects accordingly. As Krimsky and Simoncelli note, permitting such searches effectively adds to the DNA database the close blood relatives of convicts already in the database. Phenotypic profiling is the practice of attempting to predict the physical appearance of the perpetrator based on the genetic analyses of a crime scene sample. This practice raises thorny ethical and policy issues, in part because the technique sometimes purports to predict the perpetrator’s race. Although such predictions are inherently probabilistic, this may not be well understood by users or by the public. Moreover, even predictions of phenotypic traits such as hair and eye color require inquiries into ancestry, because the frequencies of genetic markers associated with these traits vary across different ethnic groups. Surreptitious sampling occurs when law enforcement officers gather DNA samples from suspects without obtaining a warrant, simply by collecting ubiquitous “shed” DNA. Krimsky and Simoncelli note that under U.S. law there is no legal protection whatsoever for such “abandoned” samples, which bear the legal status of “waste.” Moreover, courts have even upheld the use of samples obtained through deception, as in a famous case in which a suspect was tricked into providing a sample by licking an envelope. And, law enforcement aside, nothing prevents our fellow citizens from collecting our “abandoned” DNA.

Of course, not every country operates this way. Part II of the book puts the situation in the United States in perspective by surveying DNA databanking regimes in five other countries, a comparative approach also adopted by a recent volume edited by Richard Hindmarsh and Barbara Prainsack, Genetic Suspects: Global Governance of Forensic DNA Profiling and Databasing (2010). Krimsky and Simoncelli note that Germany, Belgium, Switzerland, the Netherlands and Norway mandate the immediate destruction of DNA samples after DNA profiles (which contain only a small amount of genetic information) are generated.

This policy of sample destruction emerges as perhaps the most appealing “technological fix” to civil-liberties concerns. Claims that current DNA profiles don’t invade privacy because they are based on “junk” DNA that is completely devoid of predictive value have been overstated. Nonetheless, it seems clear that contemporary law-enforcement DNA profiles provide little basis for potential genetic discrimination. Thus destruction of the DNA samples used to generate the profiles would resolve many of the most pressing threats to privacy.

At the end of the book Krimsky and Simoncelli offer a reasonable set of additional policy recommendations: Apply the same protections afforded medical records to the information held in law-enforcement biological databanks; restrict the contents of the database to profiles of felons; and require warrants for dragnets, familial searches and recovery of shed DNA. Although these are reasonable suggestions, Krimsky and Simoncelli do not offer an entirely coherent ethical vision for how to grapple with the issues raised by the advent of DNA profiling. In particular, they tend to invoke all possible criticisms—invasion of medical privacy, race discrimination and ineffectiveness—without clearly articulating which of these issues is the fatal one. This results in some inconsistency: DNA databases are grave threats to privacy despite being ham-handedly ineffective; behavioral genetic research is both a pernicious resurgence of eugenics and a doomed research program based on a faulty understanding of human differences. And, in my view, Krimsky and Simoncelli are too willing to credit genetic determinism in making their privacy arguments—too willing to perpetuate the view that “DNA sequence information may . . . contain information about behavioral traits, such as propensity to violence or substance addiction, criminal tendencies or sexual orientation.” And they are too willing to credit a study that claims to explain marital discord genetically, perhaps in hopes that the claim will help raise the reader’s hackles about genetic privacy.

Nonetheless, Genetic Justice constitutes the single most comprehensive articulation of the civil-liberties concerns associated with law-enforcement DNA databases and should, therefore, serve as a touchstone for debates about the spread of DNA profiling. David Kaye, meanwhile, is apparently working on a new book that will address privacy and civil-liberties concerns. Because Kaye is among the most vigorous defenders of the legality of government DNA sampling and storage, and is among the most persuasive advocates of a universal, population-wide DNA database, Krimsky and Simoncelli’s arguments will soon find themselves with a worthy adversary.

Simon A. Cole is associate professor and chair of the department of criminology, law and society at the University of California, Irvine. He is a coauthor (with Michael Lynch, Ruth McNally and Kathleen Jordan) of Truth Machine: The Contentious History of DNA Fingerprinting (University of Chicago Press, 2008) and is a contributor to Genetic Suspects: Global Governance of Forensic DNA Profiling and Databasing, edited by Richard Hindmarsh and Barbara Prainsack (Cambridge University Press, 2010).

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