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January 14, 2008

Low Copy Number DNA Dealt a Low Blow?

Twenty-nine people died and 200 were wounded when a 255-kilogram car bomb exploded in a busy shopping area. No, this was not Baghdad or Jerusalem. It was Omagh, Northern Ireland, in 1998. The bomb was the work of splinter group calling itself the Real IRA. It was Northern Ireland's worst single terrorist atrocity.

Ten years later, Sean Hoey, a 38-year-old electrician was on trial for the murders. It was Britain's biggest murder trial.  Justice Reg Weir, sitting under Northern Ireland's Diplock non-jury system for terrorism trials, announced his verdict last month -- not guilty! Hoey waved to applauding family members as relatives of the victims gasped in shock. Families of the dead said they were stunned that Mr Hoey had been acquitted but pledged to press ahead with a civil action for 14 million pounds compensation against five men who they claim were responsible for the attack.

Shades of O.J. Simpson? A lynchpin in the case was DNA evidence. The prosecution maintained that bombs used in various attacks, including this one, had distinctive similarities in their construction and that Hoey had been involved in constructing them. His DNA, it claimed, had been found in connection with four of them (not including the Omagh bomb). However, the judge had harsh words for the treatment of this vital DNA evidence, saying that the recording, packaging, storage and transmission of some of the items was "thoughtless" and "slapdash." He found that the police and forensic laboratory did not take "appropriate DNA protective precautions" and that the police had engaged in "mendacious attempts to retrospectively ... alter the evidence" to hide this fact.

For good measure, the court added a discussion of the validity of Low Copy Number (LCN) DNA typing. Introduced by Britain's Forensic Science Service (FSS) in 1999, LCN is a term for one of several related methods for increasing the sensitivity of ordinary DNA testing. All the procedures start by "amplifying" a sample of DNA, that is, by producing a huge number of copies of the original molecules for analysis.  LCN pushes the amplication step (known as PCR, because it is based on the Polynerase Chain Reaction for copying stands of DNA) to its limits. It permits the duplication of just a few original molecules.

The defense experts criticized LCN for want of adequate validation. They reached this conclusion because: (1) LCN results were admitted as evidence in only three countries; (2) the US (which only used it for investigative purposes) employed "a different and much more stringent operating system"; (3) it lacked "an international agreement on validation"; and (4) only two scientific papers on the technique were published, and those were written by its inventors. The judge endorsed these criticisms.

This part of the opinion seems odd for a country that does not subject scientific evidence to special scrutiny -- that has no precedent comparable to the Frye or Daubert cases in the United States. The opinion justifies its discussion of these matters by quoting from a House of Commons'committee report calling for a " 'gate-keeping' test for expert evidence [building] on the US Daubert test."

The Crown Prosecution Service responded by carrying out a "precautionary internal review of current cases involving the FSS use of LCN DNA analysis." On 14 January 2008, it reported that it could not find

anything to suggest that any current problems exist with LCN. Accordingly we conclude that LCN DNA analysis provided by the FSS should remain available as potentially admissible evidence. Of course, the strength and weight such evidence is given in any individual case remains a matter to be considered, presented, and tested in the light of all the other evidence



Queen v. Hoey, [2007] NICC 49, WE17021

Crown Prosecution Service, Press Release, Review of the use of Low Copy Number DNA Analysis in Current Cases: CPS Statement, Jan. 14, 2008, http://www.cps.gov.uk/news/pressreleases/101_08.html

Duncan Campbell and Vikram Dodd, Police Suspend Use of Discredited DNA Test after Omagh Acquittal, The Guardian, December 22, 2007, http://www.guardian.co.uk/Northern_Ireland/Story/0,,2231403,00.html

Anne Cadwallader, Omagh Bombing Suspect Acquitted, Reuters UK, Dec 20, 2007, http://today.reuters.co.uk/news/articlenews.aspx?type=topNews&storyid=2007-12-20T201408Z_01_L2062777_RTRUKOC_0_UK-IRISH-OMAGH.xml

January 14, 2008 | Permalink


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