DNA Identification Evidence in Criminal Prosecutions

In criminal cases, there have been challenges on sufficiency grounds and concerns over the use of forensic DNA evidence as the sole or primary proof of guilt. Uncorroborated DNA matching might not be enough to satisfy the burden of establishing guilt beyond a reasonable doubt. The reliability of forensic DNA testing results might be questioned for any number of reasons, e.g., laboratory error, cross-contamination, interpretive bias or fraud, etc. See generally Tarnish On the ‘Gold Standard’: Recent Problems in Forensic DNA Testing, Champion, Jan./Feb. 2006, at 10.

Studies, standards and case reviews have highlighted the types of miscalculations that can occur and undermine confidence in evidence derived from genetic matching. Every kind of problem from mathematical errors to laboratory mishaps to fakery can plague the presumptive efficacy of DNA testing. See, e.g., Already Under Fire, Crime Labs Cut to the Bone, MSNBC, Feb. 23, 2010. This article highlights recent publications that underscore the need for closer scrutiny and weighing of DNA profiling when it is offered as the principal or exclusive evidence of guilt beyond a reasonable doubt.


ABA Standards on DNA Evidence (3d ed. 2007)
“Standard 1.1 Scope of Standards

(a) For purposes of these standards, DNA evidence is biological material from which DNA is or can be extracted.

(b) These Standards are applicable to DNA evidence used for genetic identification in criminal cases.

Standard 1.2 General Principles

(a) Consistent with rights of privacy and due process, DNA evidence should be collected, preserved, tested, and used when it may advance the determination of guilt or innocence.

(b) DNA evidence should be collected, preserved and tested, and the test results interpreted, in a manner designed to ensure the highest degree of accuracy and reliability.

(c) The policies and procedures employed for testing DNA evidence should be available for public inspection.

(d) Test results and their interpretation should be reported and presented in an accurate, fair, complete, and clear manner.

(e) A person charged with or convicted of a crime should be provided reasonable access to relevant DNA evidence and, if it has been tested, to the test results and their interpretation.

(f) The collection and preservation of, access to, and use of DNA evidence should be regulated to prevent inappropriate intrusion on privacy rights.

(g) Funding necessary to achieve these principles should be provided.”

FBI DNA Laboratory: A Review of Protocol and Practice Vulnerabilities (Office of the Inspector General 2004) [PDF]
“This report describes the results of the OIG’s review. Our objectives were twofold: 1) to analyze the vulnerability of the protocols in the FBI Laboratory’s DNA Analysis Unit I (DNAUI) – the unit where Blake worked – to undetected inadvertent or willful noncompliance by DNAUI staff members; and 2) to assess the DNAUI’s application of the protocols identified as vulnerable. The report also examines and notes several areas of concern with regard to FBI management’s response to Blake’s misconduct.”


DNA for Defense (NCST)
The National Clearinghouse for Science, Technology and the Law at Stetson University College of Law (NCST) has created a bibliographic site with links to articles, books, cases and legislation on the defense issues in DNA identification.

NLADA Forensic Library: DNA

The National Legal Aid and Defender Association (NLADA) has devoted a portion of their online Forensic Library to DNA evidence, including extensive information on legal practice and scientific issues.

Reference Guide on DNA Evidence (pp. 485-576) in Reference Manual on Scientific Evidence (FJC 2nd ed. 2000)

The Federal Judicial Center’s bench book on scientific evidence has a chapter outlining the basics of DNA evidence and the threshold legal issues. Notably, the Third Edition is due to be published soon.

Using the Internet in Your DNA Case (Missouri State Public Defender)
Cynthia A. Dryden, a public defender in the Capital Litigation Unit of the Missouri State Public Defender’s office has put together an extensive collection of annotated online sources of information spanning the spectrum of DNA evidence.


Art in the Science of DNA: A Layperson’s Guide to the Subjectivity Inherent in Forensic DNA Typing, 58 Emory L.J. 489 (2008)
“[T]his Essay is about DNA typing done absolutely correctly. It is intended for the forensic science outsider – the person perhaps casually acquainted with forensic techniques – who may even suspect that bite, tool, or handwriting analyses are faulty, but assumes that DNA typing is science in its purest, most objective form. It provides an answer to questions like: why do DNA analysts often demand a suspect’s sample before reaching definitive conclusions about what profiles are contained in the crime scene sample, or why should genetic attribution statements that may be made with a high degree of confidence nevertheless not be confused with those made with absolute certainty?

This Essay proceeds as follows: Part I provides a superficial overview of nuclear DNA typing as the basis for the remainder of the discussion. Part II presents, in as clear and simple terms as possible, a sampling of the kinds of discretionary decisions that analysts often confront when interpreting crime scene samples. Part III wraps up with remarks about current disputes in forensic DNA typing, and how recognition of its inherent subjectivity might inform and illuminate these debates.”

Authentication of Forensic DNA Samples, Forensic Sci. Int. Genet., Vol. 4, Issue 2, pp. 95-103 (February 2010)
“Over the past twenty years, DNA analysis has revolutionized forensic science, and has become a dominant tool in law enforcement. Today, DNA evidence is key to the conviction or exoneration of suspects of various types of crime, from theft to rape and murder. However, the disturbing possibility that DNA evidence can be faked has been overlooked. It turns out that standard molecular biology techniques such as PCR, molecular cloning, and recently developed whole genome amplification (WGA), enable anyone with basic equipment and know-how to produce practically unlimited amounts of in vitro synthesized (artificial) DNA with any desired genetic profile. This artificial DNA can then be applied to surfaces of objects or incorporated into genuine human tissues and planted in crime scenes. Here we show that the current forensic procedure fails to distinguish between such samples of blood, saliva, and touched surfaces with artificial DNA, and corresponding samples with in vivo generated (natural) DNA. Furthermore, genotyping of both artificial and natural samples with Profiler Plus(R) yielded full profiles with no anomalies. In order to effectively deal with this problem, we developed an authentication assay, which distinguishes between natural and artificial DNA based on methylation analysis of a set of genomic loci: in natural DNA, some loci are methylated and others are unmethylated, while in artificial DNA all loci are unmethylated. The assay was tested on natural and artificial samples of blood, saliva, and touched surfaces, with complete success. Adopting an authentication assay for casework samples as part of the forensic procedure is necessary for maintaining the high credibility of DNA evidence in the judiciary system.”

Chimeras: Double the DNA-Double the Fun for Crime Scene Investigators, Prosecutors, and Defense Attorneys?, 40 Akron L. Rev. 435 (2007)
“This article first explores the mythological origins of the term ‘chimera.’ It then explores the causes and scientific explanations of chimerism and the various conditions covered by the term chimera in the area of genetics. Although this article will discuss the various chimeric conditions that are thought to exist, its primary focus is on chimerism that is the result of the fusing of embryos in utero. Next, the article will discuss recent cases of chimerism – and of alleged chimerism – and how the genetic differences between chimeras and the general population came to light. It also will discuss the implications that chimerism may have on the investigation, prosecution, and defense of criminal cases by providing hypothetical criminal scenarios involving a chimeric defendant. Finally, the article will address the possibility that chimerism may have a ‘Reverse CSI Effect’ on criminal cases.”

Convictions Predicated on DNA Evidence Alone: How Reliable Evidence Became Infallible Citation, 38 Cumb. L. Rev. 313 (2007-2008)
“When describing the moment he stumbled upon one of the most important developments in both the science and criminal justice fields, Professor Sir Alec Jeffreys remembered, ‘It was a eureka moment’. In September 1984, Jeffreys discovered DNA fingerprinting and transformed forensic identification. Years later, Jeffreys warned against ‘thoroughly dangerous’ bids to boost the power of DNA fingerprinting. Though Jeffreys recognized the significance of his ‘eureka moment,’ he questioned the ability of man to resist its misuse. It appears Jeffreys’ warning has not been universally heeded.”

Cross-Examination: Seemingly Ubiquitous, Purportedly Omnipotent, and ‘At Risk’, 14 Widener L. Rev. 427 (2009)

“Cross-examination is viewed as a core aspect of the trial process, both criminal and civil, and its use and purported power are omnipresent in the American adjudicative system. Indeed, this role is confirmed in the abundance of literature (both fictional and educational) involving cross-examination, and its increasing prominence in the law school curriculum.
This article confirms the exalted status cross-examination has achieved and arguably retains in the American trial and fact-finding process, while simultaneously identifying its frailties: its ineffectiveness as a truth-discerning tool in varying contexts; trends in constitutional law that will eliminate the requirement of cross-examination for expanding categories of witnesses; and the impact of technology and popular media on the learning processes and expectations of jurors. Particularly because of the transformation of hearsay law and the continuing trend toward visual rather than aural learning and knowledge accumulation, cross-examination may play a reduced role in the trial process and its form may need to be reinvented.”

DNA Evidence in Criminal Trials: A Defense Attorney’s Primer, 74 Neb. L. Rev. 444 (1995)
“This Article is designed to assist those criminal defense attorneys in the unenviable position of having to challenge DNA evidence in court without the advice of a scientific expert to assist in discovery, pre-trial motions, cross-examination, and trial strategy. It covers the basic science involved in DNA analysis, the history of forensic DNA evidence in criminal proceedings, and some of the strategies used in successful challenges to the admissibility of DNA evidence. The final section provides some sample questions that might be used in attacking the weight of evidence during cross-examination.”

Evaluating Forensic DNA Evidence: Part 1, The Champion, April 2003, at 16 and Evaluating Forensic DNA Evidence: Part 2, The Champion, May 2003, at 24
“The criminal justice system presently does a poor job of distinguishing unassailably powerful DNA evidence from weak, misleading DNA evidence. The fault for that serious lapse lies partly with those defense lawyers who fail to evaluate the DNA evidence adequately in their cases. This article describes the steps that a defense lawyer should take in cases that turn on DNA evidence in order to ascertain whether and how this evidence should be challenged.”

Guilt by the Numbers: How fuzzy is the math that makes DNA evidence look so compelling to jurors?, Cal. Lawyer, April 1, 2009

“Now on appeal, Puckett, along with similar cases across the country, is raising new questions and concerns over how prosecutors present DNA evidence to jurors (People v. Puckett, No. A121368, Cal. Ct. App., 1st Dist., May 1, 2008).

When you trawl through immense digitized compendiums of genetic fingerprints, ‘there is an undue risk of false matches,’ says former Food and Drug commissioner Donald Kennedy, who contributed to a recently released bombshell of a study from the National Research Council that raised serious questions about how forensic labs are administered. The science, Kennedy adds, ‘is being shut out of court.’ And even experts who say the danger of false matches is being exaggerated acknowledge that as offender databases continue to grow, the chances of convicting the innocent will only increase. “

New Forensics: Criminal Justice, False Certainty, and the Second Generation of Scientific Evidence, 95 Calif. L. Rev. 721 (2007)
“This Article challenges the new orthodoxy of forensic science. In so doing, it reframes the debate about forensic evidence in the criminal justice system in three respects. First, this Article sets forth a new taxonomy of forensic evidence, and distinguishes between first and second generation sciences by enumerating specific, classifiable characteristics. Second, using that framework, this Article illustrates how the pathologies of the criminal justice system that ultimately tarnished the first generation of forensic evidence are in fact aggravated, rather than relieved, by the particular characteristics of the second generation. Lastly, this Article criticizes current approaches to improving the use of forensic evidence in the criminal justice system for failing to account for the particular characteristics of second generation sciences, and instead advocates for changes tailored to those specific concerns.”

People v. Nelson: A Tale of Two Statistics, 7 L., Probability, & Risk 247 (2008)
“In recent years, defendants who were identified as a result of a search through a database of DNA profiles have argued that the probability that a randomly selected person would match a crime-scene stain overstates the probative value of the match. The statistical literature is divided, with most statisticians who have written on the subject rejecting this claim. In People v. Nelson, [43 Cal.4th 1242 (2008)] the Supreme Court of California held that when the random-match probability is so small as to make it exceedingly unlikely that any unrelated individual has the incriminating DNA profile, this statistic is admissible in a database-search case. In dicta, the court suggested that the defendant might be permitted to introduce an inflated match probability to counter the prosecution’s statistic. This Comment describes the statistical issue, questions some of the reasoning in Nelson, and suggests other approaches that a defendant might take in response to a cold hit in the database.”

Use of Forensic DNA Evidence in Prosecutors’ Offices, 35 J.L. Med. & Ethics 310 (2007)
“Prosecutors report seeing DNA as a powerful prosecutorial tool. At the same time there appears to be a consensus among practitioners and informed observers that the full promise of DNA within the criminal justice system has yet to be realized. Thus, given the role of the prosecutor in developing patterns of DNA testing and its use in charging, trying, and convicting alleged criminals, it behooves us to learn more about how this technology has been integrated into the daily activities of the nation’s 2,800 prosecutors’ offices. Because little information exists on the nature or pattern of ordinary practice, we carried out a survey-based study of the DNA-related practices and procedures within District Attorneys’ (DA) offices to obtain a ‘snapshot’ of preliminary information about actual prosecutorial practices. The data obtained is preliminary in nature, but in our estimation, it is supportive of further study of areas targeted by the survey.”

Why a Conviction Should Not Be Based on a Single Piece of Evidence: A Proposal for Reform, 48 Jurimetrics 43 (Fall 2007)
“This article illustrates a serious flaw in the conventional legal approach enabling a conviction based solely on one piece of evidence. This flaw derives from a cognitive illusion referred to as ‘the fallacy of the transposed conditional.’ People might assume a low error rate in evidence only leads to a small percentage of wrongful convictions. We show that, counterintuitively, even a very low error rate might lead to a wrongful conviction in most cases where the conviction is based on a single piece of evidence. Case law has indicated some awareness of this fallacy, primarily when considering the random match probability for DNA evidence. However, there is almost no awareness of the significance of this fallacy in assessing other types of evidence not considered probabilistic or of the significance of laboratory errors in DNA testing. We show that mistakes do happen with all key types of evidence: fingerprints, DNA, confessions, and eyewitness testimony. We then demonstrate the tremendous impact that even a small probability of error has on our confidence in a conviction. In the end, we propose legislative reform that would make it impossible to convict someone on the basis of any single piece of evidence linking him to a criminal offense.”


Danger of DNA: It Isn’t Perfect, Los Angeles Times, Dec. 26, 2008
“DNA has proved itself by far the most effective and reliable forensic science. Over the last two decades, it has solved crimes once thought unsolvable, brought elusive murderers and rapists to justice years after their misdeeds and exonerated the innocent. In courtrooms and in the popular imagination, it is often seen as unassailable. But as the nation rushes to take advantage of DNA’s powers, it is becoming clear that genetic sleuthing also has significant limitations.”

DNA Evidence Can Be Fabricated, Scientists Show, New York Times, Aug. 17, 2009
“Scientists in Israel have demonstrated that it is possible to fabricate DNA evidence, undermining the credibility of what has been considered the gold standard of proof in criminal cases.”

DNA Research Commons Scaled Back, American Scientist, March-April 2009
“Concerned about violating DNA donor confidentiality, U.S. research agency sticks with decision to limit data exchange

The U.S. government’s heralded plan to help researchers freely share some genetic research data online to speed up disease research is now a dream deferred.

The National Human Genome Research Institute is sticking with a decision, made last summer, to remove free-access, pooled genomics data it started posting on the Internet in 2006. Other high profile research organizations, including the Broad Institute, are doing the same.

The retreat began after investigators at Arizona’s Translational Genomics Research Institute and colleagues discovered how to detect individual genetic profiles in pools of 1,000 or more DNA donors. Their bioinformatics tools are so brawny that they produced positive donor IDs even from averaged data alone, which were all that the institute was sharing freely.

Geneticists, like all scientists, usually champion data sharing. But people who donate DNA for research studies typically are assured that their identities will remain confidential. Government officials were no longer certain they could keep that promise.”

DNA Statistics Found Insufficient to Convict Without Corroboration, Forensic-Evidence.com: Evidence Law News (Oct. 19, 2000)
“In most criminal prosecutions where DNA evidence is utilized, the evidence serves to corroborate, in a powerful manner, other circumstances pointing to the guilt of the accused. But should DNA evidence alone be sufficient to convict when there is no corroborative evidence, except of the most generalized and non specific nature? A recent U.K. decision [R v Watters [2000] EWCA Crim 89 (19th October 2000)] held that DNA evidence, without corroborating evidence, was not sufficient evidence to convict under the particular circumstances of the case.”

DNA’s Dirty Little Secret, Washington Monthly, March/April 2010
“A forensic tool renowned for exonerating the innocent may actually be putting them in prison.”

FBI and States Vastly Expand DNA Databases, NY Times, April 18, 2009
“Until now, the federal government genetically tracked only convicts. But starting this month, the Federal Bureau of Investigation will join 15 states that collect DNA samples from those awaiting trial and will collect DNA from detained immigrants — the vanguard of a growing class of genetic registrants.

The FBI, with a DNA database of 6.7 million profiles, expects to accelerate its growth rate from 80,000 new entries a year to 1.2 million by 2012 — a 15-fold increase. FBI officials say they expect DNA processing backlogs — which now stand at more than 500,000 cases — to increase.”

Genetic Surveillance for All, Slate, March 17, 2009
“All of this could mean a slew of legal challenges on the horizon—not only over familial searching but also over the decision to include people who have been arrested in DNA databases at all, as 14 states and the federal government have done. In December, the European Court of Human Rights held that Britain’s decision to store the DNA of unconvicted people violates European privacy guarantees—throwing the future of the British database into question.

The legal limits on family searches and DNA databases are murky, but the political implications are explosive for one big reason in particular: race. African-Americans, by several estimates, represent about 13 percent of the U.S. population but 40 percent of the people convicted of felonies every year. The CODIS database of 6.6 million now includes samples from convicted offenders. As arrestees are added to this mix, CODIS may soon grow to 50 million samples, which might be even more disproportionately African-American. Hank Greely of Stanford Law School has estimated that 17 percent of African-American citizens could be identified through familial searches, as opposed to only 4 percent of the Caucasian population. Once the implications of the racial disparity become clear, there may be a reaction against ever-more-expansive forms of DNA collection that makes the debate about racial profiling look tame.”

Release State DNA Profiles, Los Angeles Times, July 27, 2008
“The FBI is correct — DNA database searches, with their seemingly surprisingly large number of matches, do not invalidate its claims. But rather than block these searches through bullying, the FBI should get a court ruling that large numbers of matches in such searches do not invalidate the methods used and therefore cannot be introduced as evidence to cast doubt on the reliability of DNA matches in crime investigations.

If we are going to convict people of crimes on the basis of DNA evidence, there is no excuse for blocking research into its accuracy. If juries discover the FBI is preventing research into the accuracy of DNA evidence, they almost certainly will conclude that the accuracy is not what the FBI claims, and they will discount or ignore the evidence.”

To Sketch a Thief: Genes Draw Likeness of Suspect, Wall St. J., March 27, 2009
“Researchers are identifying genes that give rise to a person’s physical traits, such as facial structure, skin color or even whether they are right- or left-handed. That could allow police to build a picture of what a criminal looks like not just from sometimes-fuzzy eyewitness accounts, but by analyzing DNA found at a crime scene.”

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