Bedazzled by DNA - is it enough to convict?

Over a period of four months the police obtained blood samples from more than 50 people. Forty-nine-year-old Andrew Fitzherbert was the last person tested.

Fitzherbert, then aged 49, had no criminal record and those who knew him described him as a pacifist. An acclaimed palm reader, with three books on palmistry published, he did readings from his home in Zillmere and also helped his partner, Ruth Bennett, run the Windsor spiritualist church.

Houston had gone to the church for several years to get psychic readings. Fitzherbert later said in court, “Virginia would go on endlessly about the [Cat Protection] society and its disputes”. It was Houston who suggested they join the society for she needed support of “goodies”, as opposed to “baddies”, to overcome the corruption. Bennett became a member in May 1997.

On Wednesday, July 1, 1998, Detective Geoffrey Marsh seized a number of items from Fitzherbert’s house. On the basis of DNA found on a handkerchief, and despite having an alibi, Fitzherbert was arrested that Saturday.

On the Friday, February 28, the likely time of the murder, Fitzherbert and Bennett attended a meditation circle with friends and then visited Bennett’s daughter, Cathryn Beck. Bennett said they arrived home well after midnight and went straight to bed. “To think Andrew sneaked out, drove to Marshall’s and for some reason killed her is ridiculous. At that time Marshall would be wearing nightclothes, not the day clothes they found her in. Why would she let him in at that hour? He didn’t even know her.”

Marshall’s house was about a 20-minute drive from their home. At the time of the murder, Fitzherbert’s car was in a garage getting some repairs and they were using Bennett’s car. At no time did the police conduct an examination of the car to search for bloodstains or a weapon.

The hearing began in July 1999 in the Brisbane Supreme Court. The cornerstone of the defence was DNA evidence given by Ken Cox, a forensic biologist from the John Tonge Centre - a laboratory with a history of errors.

At the time Cox did the testing for this case, the John Tonge Centre had not obtained accreditation from the National Association of Testing Authorities. Indeed, in late 1998, NATA’s investigations discovered shortcomings including poorly documented records, unsealed evidence, unrestricted access to specimens and potentially contaminated specimens in the refrigerator.

Cox gave the jury a background to DNA analysis, and went on to give a lengthy explanation of loci, alleles and probabilities in relation to the scene samples and Fitzherbert’s blood profile. He concluded there was “one chance in 14 trillion the blood found at the crime scene was from someone other than Fitzherbert”.

This staggering probability of one in 14 trillion is very impressive and persuasive, given that the population of the Earth is about 6.5 billion, but is it accurate?

Fitzherbert’s lawyer, Laura-Leigh Cameron-Dow of Slater & Gordon says the DNA results do not support this probability. “I’ve been given alternate (sic) estimates from other experts of 1 in 100,000,” she says. “Ken Cox included test results in his analysis that shouldn’t have been recognised in court as reliable. The defence didn’t query Cox as to whether the results received from samples were strong enough to be recorded as positives under scientific guidelines established for use of DNA evidence in the courtroom.”

Professor Barry Boettcher, influential in uncovering problems with evidence in the Azaria Chamberlain case, also disputes Cox’s interpretations. “Cox’s estimate might be out by a factor of a million. There is just no possibility of determining the accuracy of the figure given to the jury. But it would have sounded highly impressive to them.”