Saturday, December 22, 2007
In what appears to be the across the pond equivalent of the FBI lead bullet analysis fiasco, the United Kingdom has suspended its use of "low copy number" DNA. Low copy number DNA allows the genetic profiles of suspects, victims or witnesses to be "uncovered" even when there is only a tiny amount of biological material present, sometimes as small as a milionth of the size of a grain of salt. The technique amplifies these tiny DNA fragments when it is believed that a suspect may have transferred DNA through touch, like the residue believed to have come from cells such as skin or sweat left in a fingerprint.
Since this technique was launched in 1999, it has been consistently doubted in the scientific community, and it has thus only been used in the U.K., the Netherlands, and New Zealand. Nonetheless, it has found popularity in the U.K., being used 21,000 times in its nine years of existence. That popularity now looks like a pernicious mistake which should result in an avalanche of appeals by criminals who were convicted using the method.
This avalanche is likely to come as a result of the acquittal of Sean Hoey, the only man charged in connection with the Omagh car bombing. The prosecution in Hoey's case used low copy number DNA evidence to link him to some of the explosive devices used in the bombing. The judge in the Hooey case, Mr Justice Weir, found that Hoey was not guilty and was extremely critical of the evidence, noting how few countries use it and how it had been used to wrongly link a 14 year-old schoolboy to a bomb in Lisburn. In the wake of the Hoey case, the Crown Prosecution Service ordered a re-examination of current cases relying on low copy number DNA evidence, and the Association of Chief Police Officers has suspended its use of it.
To me, the Hoey case brings to mind the Moe Gibbs case. In the Gibbs case, a key piece of the prosecution's case was expert testimony that the amount of DNA evidence belonging to Gibbs found under the victim's fingernails was the result of "vigorous physical contact" between the two and not the result of a secondary transfer which might have resulted from the two touching a common item. Other courts, however, have found that similar proposed expert testimony is inadmissible as overly speculative. It seems to me that it's only a matter of time before the type of expert testimony used in the Gibbs case is found to be unacceptably unreliable.