Sunday, July 20, 2014

Stopping a Defendant from Using a DNA Database Trawl to Blame Someone Else in Diggs v. State

A violent burglary and robbery of two unsavory characters in their apartment near Rockville, Maryland, led to felony charges against two men, Allen and Diggs. Near the apartment, police recovered various items that seemed to be associated with the robbery. These included a Pittsburgh Pirates baseball hat and a black bandana that the robbers apparently had worn.

At their trial, Allen and Diggs called a single witness—“Naomi Strickman—a forensic specialist with the Montgomery County Crime Laboratory” to prove that a database search linked the DNA on these items to two other men named Bangora and Debreau. The prosecutor successfully objected that a Maryland statute made the database matches inadmissible.1 In Diggs v. State,2 the Maryland Special Court of Appeals affirmed and upheld the convictions.3 It endorsed the prosecution's reading of the statute's exclusionary rule.

But was the statute really designed to exclude a defendant’s evidence that a DNA database trawl produced other possible suspects? The statute provides that “[a] match obtained between an evidence sample and a data base entry may be used only as probable cause and is not admissible at trial unless confirmed by additional testing.”

This “additional testing” is not necessarily any different or any more accurate than the original testing. It normally consists of replicating the match to the crime-scene evidence with the same technology (or perhaps a more efficient variation on it) applied to a fresh DNA sample from the individual whose recorded profile matched. Such retesting is useful because it establishes that there was no bookkeeping error in entering the DNA record into the database and no laboratory error in determining the recorded profile. Checking the database match with a fresh sample is easily done, because the database match supplies probable cause to obtain the new sample and thereby verify that the profile on record really came from the individual whose name is on the record.4

If the state can rely on the database evidence for probable cause before trial, why cannot the defense rely on it for the same inference at trial? The court’s answer is “plain meaning.” The statute says “not admissible at trial” rather than “not admissible at trial when introduced by the prosecution.” But if the statute’s purpose is to avoid a conviction based on a clerical or laboratory error that can be easily caught by requiring the prosecution to confirm the database match, it is not so plain that it also was meant to force defendants to collect fresh DNA samples from people the state believes are innocent and test them to check the state’s work.

The Diggs court assumed that the dominant purpose of the provision is to ensure that the state uses “the most recent scientific and technological methodologies available” at trial. For some reason, the court thought that the confirmatory test is needed to produce further individualizing information, changing what was a mere probability to a near certainty. Judge Kehoe wrote that
A CODIS match probably, but does not always, mean that the two DNA samples represented by the DNA records came from the same person. ... [A]dditional analysis and testing is then completed on the DNA samples in order to determine whether the physical samples, themselves, “match”—i.e., whether, after the physical samples have been tested, compared, and analyzed, they are verified (to a near certain degree) to be from the same person.
But the statute does not mandate more extensive testing. It applies before any new equipment or procedures come on line. And, even if the state has a newer set of loci or fancier machinery, the words of the statute do not stop a state from using the older technology to confirm the database match.

Of course, it is possible that the confirmatory testing will include additional loci, but a 13-locus match is quite powerful evidence. For many years, it has been more than enough to seal the fates of thousands of defendants. Surely exculpatory evidence from the defense need not be more probative than that. Indeed, evidence that only generates “probable cause” to believe that someone else is responsible for the crime should be enough to inject a reasonable doubt into the proceedings.

Ignoring this asymmetry in the criminal process, the court asserts that the legislature's original intent was not just to ensure that before the state tries a defendant located through a database trawl, it checks that the database match was accurate. Displaying a certain suspicion of the third-party defense, the court attributes to the legislature an intent to render evidence inadmissible “at trial by a defendant as a mechanism to mislead, confuse, or otherwise distract the jury” .

However, a statutory exclusionary rule intended to protect defendants from false database matches is unnecessary to handle abuses of the third-party defense. The normal rules of evidence give the trial judge ample discretion to exclude testimony when there is so little substance to the defense theory that dragging innocent people whose DNA was in the database into the case would be unduly time-consuming and distracting. Interpreting the Maryland statute to encompass the defensive use of DNA database matches is unnecessary to protect against jury confusion or distraction. If the DNA evidence meets the ordinary standards of relevance and scientific validity, it should be admissible.

  1. Md. Code Ann. Public Safety § 2–510 (2003, 2009 Supp.).
  2. 73 A.3d 306 (Md. Ct. Spec. App. 2013).
  3. The opinion contains a meandering description of forensic DNA evidence. Although mitochondrial DNA has nothing to do with the case, the opinion launches into a discussion of mitochondrial testing. Among other things, it states that
    Human cells contain two genes capable of being analyzed for DNA: mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). ... Mitochondrial DNA is the smaller of the DNA genes and is found within an organelle called the mitochondrion which floats “in the cytoplasm surrounding the nucleus of a cell.” ... Nuclear DNA is the larger of the DNA genes.
  4. The names are actually stored separately to protect the privacy of the individuals whose DNA is in the databank.

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