Scientists sceptical of Holohan DNA testing
Technology used in the trial of Wayne O'Donahgue is 'a very dangerous test.' By Colin Murphy
Scientists at the forensic science service of South Australia and at the US Federal Bureau of Investigation (FBI) have questioned the validity of the type of DNA testing used in the investigation of the killing of Robert Holohan.
Katrin Both, who is the senior forensic scientist at the Forensic Science Centre in Adelaide, said the technology used by the UK laboratory to test semen found on Robert Holohan's hand had not been adopted worldwide because of concerns about its reliability.
Katrin Both described the technology as "a very dangerous test". "It's pushing the boundaries (of science) to the utmost limits", she said. And the senior scientist at the FBI's laboratory division, Bruce Budowle has said that, in using this technology, "the success rate is low; often the results cannot be interpreted or are meaningless for the case".
A semen sample taken from Robert Holohan's hand by the State Pathologist, Marie Cassidy, was sent to the UK's Forensic Science Service (FSS) laboratory at Wetherby in Yorkshire.
Since 1999, under Jonathan Whitaker, the FSS has pioneered a type of DNA analysis known as low copy number (LCN) typing. This is a DNA test of greater sensititivy, which allows smaller samples to be tested than in traditional analysis.
According to reports on the Wayne O'Donoghue case, Jonathan Whitaker initially concluded that there was a one in 70 million chance that the semen sample had not come from Wayne O'Donoghue. On the basis of this finding, the Director of Public Prosecutions (DPP) changed the charge against Wayne O'Donoghue from manslaughter to murder.
Then a further semen sample was taken from a bathroom mat in the O'Donoghue house and forwarded to Whitaker. This wasn't identical to the first sample, and led Whitaker to change his first report.
Wayne O'Donoghue's solicitor, Frank Buttimer, sought a second opinion; forensic experts he consulted disputed Jonathan Whitaker's initial report. The DPP withdrew the forensic reports on the semen from the book of evidence, and they were not referred to at the trial. However, following Majella Holohan's comment at the end of her victim impact statement on 24 January that semen was found on Robert Holohan's body, there has been widespread media and public comment about the DNA analysis of the semen, and whether it should have been used as evidence (see article on page 24).
Katrin Both said the sensitivity of the LCN technology was so great that DNA material from different sources could easily be mixed up. In a case where it was not clear that the DNA came from one particular source, this technology was unreliable, she said.
In the case of Robert Holohan, she said, it was likely that the DNA sample from Robert Holohan's hand could have been contaminated by sweat or skin cells from Wayne O'Donoghue.
She said the sensitivity of the technology was such that it was very credible that the semen could have been transferred from the bathroom mat. She also said that semen was highly resistant to environmental factors and that the sample would be unlikely to deteriorate significantly due to exposure to the elements. She said in cases that she had dealt with, where sexual abuse had occurred, there was typically a very large amount of DNA material available for analysis.
Both said the LCN method was so sensitive that it could detect DNA where "there could have been casual or innocent contact between the victim and suspect, not related to the crime in question".
Low copy number DNA analysis has also been criticised by the senior scientist at the US Federal Bureau of Investigation's (FBI) laboratory division, Bruce Budowle.
Urging "caution" with its use, Budwole has said that, in using this technology, "the success rate is low; often the results cannot be interpreted or are meaningless for the case".
He said that LCN analysis could be warranted in "some limited applications... such as some investigative lead situations", but cautioned against its use in court. In cases where evidence obtained using LCN analysis was to be used in court, he recommended that its "limitations" should be "disclosed to all involved, including other lab personnel, supervisors, police, lawyers, the court, and even the public".
"Publicising the potential of the application of LCN typing without describing its limitations may cause misunderstanding", he said.
Budwole's comments were contained in an article published by the FBI laboratory division.
Jonathan Whitaker was not avilable for comment. Staff at the Forensic Science Service referred us to a "fact sheet" on low copy number typing on their website (www.forensic.gov.uk). It says:
"Given its increased sensitivity, DNA LCN can be a particularly useful tool for investigating serious crimes where other profiling techniques have been exhausted or when options for forensic evidence appear to be limited. For example, when there is a very small amount of material present...
"As with all forensic evidence, the context and interpretation need to be considered carefully. This is even more important with DNA LCN, due to its sensitivity and the possibility that the DNA detected is unconnected with the offence under investigation."