Monthly Archives: December 2012

“Human Error, Bias, and Malfeasance” in DNA Databases and Law Reviews

A new article in the Boston University Law Review offers the following warning:

[E]xpansive police arrest authority–and the desire to continually enlarge identity evidence databases at very little cost in time and expense–should give pause for several reasons. First, contrary to common public perception, DNA is not infallible. Rather, like other evidence, it is subject to human error, bias, and malfeasance, and has figured in several wrongful accusations and convictions. As Professor David Kaye notes in his recent book:

How probable is it that two, correctly identified DNA genotypes would be the same if they originated from two unrelated individuals? By definition, [such matches] do not consider any uncertainty about the origins of the samples (the chain-of-custody issue), about the relatedness of the individuals who left or contributed the samples (the identical-alleles-by-descent issue), or about the determination of the genotypes themselves (the laboratory-error issue).

Wayne A. Logan, Policing Identity, 92 B.U. L. Rev. 1561, 1580-89 (2012) (footnote numbers omitted).

Having searched without success for a single case in the U.S. of a false conviction based on DNA evidence from a database search,1 I was puzzled. Could I have missed several false convictions arising from erroneous DNA testing? Did these cases involve database trawls, where observer “bias” is not normally an issue?

Being a lawyer, I did what any reader of law review articles must do. I turned to the footnotes. The footnote on false convictions as a reason to constrain DNA databases reads as follows:

See Greg Hampikian et al., The Genetics of Innocence: Analysis of 194 DNA Exonerations, 12 Ann. Rev. Genomics & Hum. Genetics 97, 107 (2011) (mentioning existence of at least fifteen exonerations in which DNA resulted in conviction).

If Professor Logan (and the source-citation reviewers of the Boston University Law Review) are correct, Professor Hampikian discovered at least 15 cases of DNA evidence that resulted in false convictions. How could I have missed all these case in my earlier postings?

The Genomics and Human Genetics review article plainly does not even begin to support the claim that DNA testing produced 15 false convictions. It merely states that among previously analyzed cases of postconviction exonerations, “there were at least 15 cases where DNA was tested prior to conviction.” Hampikian et al., supra, at 107. Let’s look at the outcomes of this DNA testing, as presented by Dr. Hampikian and his colleagues:

  • The cited article does not even discuss the outcome of the DNA tests in two of the 15 cases because there were no “transcripts or other accurate information on the DNA results available.” Id. Counting two cases on which there is no information as showing that contemporary DNA databases produce false convictions is surprising.
  • “The majority of these cases included proper testimony, with DNA results that excluded the exoneree (9 of the 13 cases). These exclusions were explained away by the state in various ways–perhaps the defendant had an unknown codefendant, the DNA could have come from a consensual sex partner, etc.” Id. Claiming that DNA databases should be constrained because most DNA typing accurately showed that a defendant was not the source of an incriminating sample is inane.
  • “In 5 of the 13 cases, DQ alpha tests included the exonerees as possible contributors. In 4 of these 5 cases, however, more discriminating tests performed postconviction excluded the exonerees. In the remaining case, a second round of DQ alpha testing exonerated the defendant after it was discovered that the original lab analysis was incorrect.” Id. Before the DQA test was retired from forensic DNA testing, it was known to be relatively undiscriminating. See, e.g., Cecelia A. Crouse, Analysis of HLA DQ alpha Allele and Genotype Frequencies in Populations from Florida, 39 J. Forensic Sci. 731 (1994); NFSTC, DNA Analyst Training. Questioning databases stocked with CODIS profiles because a different, bi-allelic locus has different properties is silly.
  • “There were four cases where improper DNA testimony was given at trial. In one, the analyst testified about a match based on DQ alpha testing; however, the analyst did not disclose that it was only a partial match. In another case, the analyst did not provide the proper statistic for the population included by the results of DQ alpha testing.” To be sure, “improper” testimony is deplorable, but it is not clear that the analyst in the first case incorrectly stated the implications of the match or, more importantly for worries about databases, that analysts working with database matches would give incorrect estimates of genotype frequencies.
  • “In a third case, the analyst testified that the DNA matched the exoneree, but failed to disclose an additional exclusionary DNA result.” Withholding exculpatory evidence of any sort–DNA, fingerprint, toolmark, eyewitness, or anything else–is unconscionable and unconstitutional. But it is not much of an argument against inclusive DNA databases.
  • “In the final case, the analyst misinterpreted the results of the testing (which was performed incorrectly–failing to separate the male and female DNA during differential extraction), falsely including the exoneree as a source of the DNA when in fact he should have been excluded.” Yes, if crime-scene DNA is mistyped, and if this error goes unnoticed, a database match could result.

Can DNA databases produce false convictions? Of course they can. Police can commit perjury about DNA evidence, just as they can about other evidence. If there were no databases, it might be slightly harder to fabricate such impressive evidence. DNA evidence, like all evidence, “is subject to human error, bias, and malfeasance.” So are law review articles. (And so are blog postings–corrections are welcome).


1. David. H. Kaye, Have DNA Databases Produced False Convictions?, Forensic Science, Statistics, and the Law, July 7, 2012 (cross-posted to The Double Helix Law Blog); David H. Kaye, Genetic Justice: Potential and Real, Forensic Science, Statistics, and the Law, , June 5, 2011 (cross-posted to The Double Helix Law Blog).

Cross-posted to Forensic Science, Statistics, and the Law.

The Department of Justice and the Definition of Junk DNA

In drafting an amicus brief in Maryland v. King, the case in which the Supreme Court is reviewing the constitutionality of routine collection of DNA before conviction, I decided it is important to clarify the term “junk DNA” if only because it gets tossed around in so many court opinions and briefs. The Department of Justice defines “junk DNA” as “[s]tretches of DNA that do not code for genes.” U.S. Dep’t of Justice, Nat’l Institute of Justice, DNA Initiative Training for Officers of the Court, Glossary, (last visited Dec. 17, 2012). In scientific discourse, however, DNA does not “code for genes.” Rather, parts of genes encode proteins and RNAs. “Junk DNA” is not a synonym for the rest of the genome. It is a provocative and deprecated term for that “fraction of DNA that has little or no adaptive advantage for the organism.” Sean R. Eddy, The C-value Paradox, Junk DNA and ENCODE, 22 Current Biology R898 (2012). Some of what NIJ thinks is “junk DNA” is important to fitness. It is not “junk.”

NIJ’s sloppy treatment of terms like “genes” and “junk” is unfortunate, but in the end I decided the awkward definition was not important enough to snipe at in the brief. On a blog, however, one can be more snippy.

Crossposted to Forensic Science, Statistics, and the Law.

Reconsidering the “Considered Analysis”: How Convincing Are the Cases Cited in the Stay Order in Maryland v. King?

For nearly a decade, DNA-on-arrest laws eluded scrutiny in the courts. For another five years, they withstood a gathering storm of constitutional challenges. In King v. State, 42 A.3d 549 (Md. 2012), however, the Maryland Court of Appeals reasoned that usually fingerprints provide everything police need to establish the true identity of an individual before trial and that the state’s interest in finding the perpetrators of crimes by trawling databases of DNA profiles is too “generalized” to support “a warrantless, suspicionless search.” The U.S. Supreme Court reacted forcefully. Even before the Court could consider issuing a writ of certiorari, Chief Justice Roberts stayed the Maryland judgment. His chambers opinion signaled that “given the considered analysis of courts on the other side of the split, there is a fair prospect that this Court will reverse the decision below.”

Some thoughts on the lower court opinions and the issues the Supreme Court will confront are in press in the online Discourse section of the UCLA Law Review. The essay provides a more coherent, complete, and polished presentation than the scattered remarks in earlier postings on this blog. It briefly examines four sets of opinions–the early one from the Virginia Supreme Court in Anderson, the Third Circuit’s en banc opinions in Mitchell, the Ninth Circuit’s panel opinions in Haskell (vacated to make way for en banc review), and the Arizona Supreme Court’s opinion in Mario W. Building on these judicial efforts, the essay outlines the Fourth Amendment questions that a fully considered analysis must answer, identifies questionable treatments of “searches” and “seizures” in the four sets of opinions, and criticizes the creative compromise in Mario W. that allows sample collection but not DNA testing before conviction.

I do not think that there is much room for compromise on the constitutional question. A couple of opinions maintain (in dictum) that preconviction collection is acceptable after, but not before, an indictment or preliminary hearing. That’s another compromise, of sorts, and the Maryland law (as the state has implemented it) postpones DNA collection until after a probable-cause-for-trial hearing. Thus, anything the Supreme Court will say in King on DNA collection as part of the booking procedure will be dictum. It seems to me, however, that once an individual is legitimately detained, either the Fourth Amendment permits the compulsory collection, analysis, and use of DNA–the whole ball of wax–as a biometric identifier for both authentication and criminal intelligence purposes or it does not.  Thus, I am betting that the Court will write a broad opinion upholding DNA database laws at all points after arrest.  But IMHO, it’s a close question.


David H. Kaye, On the “Considered Analysis” of Collecting DNA Before Conviction, 60 UCLA L. Rev. Discourse (forthcoming 2013) (preprint)

David H. Kaye, Drawing Lines: Unrelated Probable Cause as a Prerequisite to Early DNA Collection, 91 N.C. L. Rev. Addendum 1 (2012) (preprint)

Crossposted to Forensic Science, Statistics, and the Law.