Saturday, July 7, 2012

Have DNA Databases Produced False Convictions?

About a year ago, I asked whether any false convictions have resulted from DNA database searches [1]. Of course, if there are any, they might be hard to find, but there is a known recent case of a false initial accusation. It came about because a laboratory contaminated a crime-scene sample with DNA from an whose DNA was on file from other cases.

In March 2012, a private firm in England re-used a "plastic tray[] as part of the robotic DNA extraction process" [2]. The tray, which should have been disposed of, apparently contained some DNA from Adam Scott, a young man from Exeter, in Devon [3]. This DNA contaminated the sample from the clothing of a woman who had been raped in a park in Manchester. Police charged Scott, who vehemently protested that he had never been to Manchester, with the rape. After detectives realized that Scott "was in prison 300 miles away, awaiting trial on other unrelated offences" at the time of the rape, the charges were dropped [3]. An audit and investigation of 26,000 other samples analyzed after the robotic system had been introduced, uncovered no other instances of contamination. Steps intended to prevent a repetition of the error have been implemented [3].

Other errors in handling samples have been documented. In a 2001 Las Vegas case, police obtained DNA samples from two young suspects, Dwayne Jackson and his cousin, Howard Grissom. A technician put Jackson's sample in a vial marked as Grissom's, and vice versa. A falsely accused Jackson then pleaded guilty and was imprisoned for four years. The error came to light in 2010, after Grissom was convicted of robbing and stabbing a woman in Southern California. California officials took Grissom's DNA and entered the profile into the national database, leading to a match to the crime-scene DNA from the 2001 burglary for which Jackson had been falsely convicted [4].

Of course, this is not a case of a DNA database hit producing a conviction or even a false accusation. Quite the contrary, it is a case of a DNA database producing an exoneration that would not have occurred otherwise. But both cases vividly illustrate the need to implement quality control systems that reduce the chance of handling and other errors and to avoid over-reliance on cold hits.

Added July 9, 2012

Jeremy Gans's comment, posted this morning, is required reading.


1. David H. Kaye, Genetic Justice: Potential and Real, The Double Helix Law Blog, June 5, 2011.

2. BBC News, DNA Blunder: Man Accused of Rape After Human Error, Mar. 21, 2012.

3. Simon Israel, DNA Contamination Blamed on Human Error, Channel 4 News, May 9, 2012.

4. Lawrence Mower & Doug McMurdo, Las Vegas Police Reveal DNA Error Put Wrong Man in Prison, Las Vegas Rev.-J., July 8, 2011.

Cross-posted from The Double Helix Law Blog.

1 comment:

  1. Australia had an instance of a false conviction that was due to a DNA database match fairly recently. It is the case of Farah Jama, who was convicted of rape in a trial in Melbourne, Victoria in 2008 and served a year in prison, before being cleared in late 2009.

    The case involved a woman who was found unconscious in a nightlcub toilet. She was taken to a rape crisis centre in a Melbourne hospital and was given a rape kit. The vaginal swab contained a single sperm and some fragments, yielding a male DNA profile. Although the woman could not remember what had happened, this finding was taken to be a confirmation of rape, as she had not had sex in some time, A few months later, the profile was matched to a sample that had been taken from Farah Jama a few months earlier when he was the subject of a different rape allegation. That allegation had already been withdrawn by then; however, in Victoria, such a profile can nevertheless remain on the database for a year after the sample was first taken.

    At his trial, Jama denied all the charges and his entire family provided an alibi. However, the jury convicted him on the basis of the DNA match (and, perhaps, his possibly false denial of ever having been in any nightclub.) But, prior to his appeal, the prosecution realised another link between Jama and the nightlclub incident. The link was that both the complainant in the withdrawn allegation (who had Jama's semen in her hair) and the woman in the nightlclub incident had attended the same rape crisis centre one day apart. This raised the possibility that Jama's DNA was transferred from the first complainant to the swab from the second one. Everyone now accepts that this is almost certainly what happened, as there was no other evidence linking Jama to the rape, and the prosecution theory of the rape was actually so unlikely (the nightlclub was an 'over 30s' event packed with Caucasians, while Jama is a Sudanese-origin teenager), and the rape crisis centre lacked adequate anti-contamination processes, . Indeed, there was almost certainly no rape at all. Jama was acquitted on appeal and given $1M ex gratia compensation.

    Obviously, the immediate blame for the false conviction (and false perception that the woman had been raped) is contamination. However, the conviction could never have occurred without a DNA database, as Jama was never even remotely a suspect for the nightclub incident. Disturbingly, although the error was discovered within a year and prior to Jama's first appeal, the discovery of the error appears to be serendipitous (based on the coincidence that the same doctor attended both women.) It is easy to imagine scenarios where the error wouldn't ever have been discovered. Although Victoria has acquired a reputation for being prone to contamination (with at least two other cases of lab contamination in the past decade, one leading to an arrest), it is otherwise a strong jurisdiction in terms of trial processes, with reasonably independent prosecutors and judges, and relatively well resourced defence lawyers and courts.

    An official report on the error is available here: I have a slightly different take in a chapter of a recently published book (Hunter & Roberts, Criminal Evidence and Human Rights, Hart, 2012.) For a short summary, see the following online article: