By Peter Gregory, Richard Baker and Tom Arup
VICTORIA Police has begun searching thousands of crime files for possible contamination of evidence after an embarrassing DNA blunder forced the abandonment of a double murder "cold case".
Weeks after crediting DNA technology with a breakthrough in the 24-year-old case, police yesterday announced they had withdrawn the charges against Russell John Gesah because the evidence they were relying may have been contaminated.
Mr Gesah, 43, was charged last month over the murders of mother and daughter Margaret and Seana Tapp at Ferntree Gully in 1984.
With the collapse of the case, lawyers yesterday accused police of having rushed to name Mr Gesah and said they might have left open an avenue for him to sue for negligence.
The acting head of the police forensics division, John Scheffer, last night denied he had found out only yesterday about the concerns, after sources told The Age that staff did not learn of the review until police announced it.
Lawyers who had represented Mr Gesah in the case said last night they could not comment because they had not yet been able to speak to him.
Police Deputy Commissioner Simon Overland told a press conference that it was embarrassing to have to make the announcement. But he said the charges had been dropped after a laboratory review identified possible contamination of biological evidence.
He said police had already reviewed 500 of 7000 other criminal cases - some of which are believed to be high-profile rape and murder cases - in a bid to identify whether other potential problems had been undetected. He said the checks had identified no further difficulties.
Such contamination would not occur today because of more stringent cleaning processes in line with more sensitive DNA testing systems, he said.
Margaret Tapp, 35, and Seana, 9, were found murdered in their home in August 1984. Police said last month that both had been strangled.
The case is not the first in which DNA evidence has been contaminated. In 2003, Mr Scheffer told an inquest on Moe toddler Jaidyn Leskie that since late 1999, 39 cases had been identified as requiring "diagnostic and corrective action", with most involving contamination.
In the Leskie case, unrelated DNA from a rape victim was found on the toddler's clothing during a 2003 check of the centre's DNA database.
Commenting on this in his October 2006 Leskie inquest findings, Coroner Graeme Johnstone concluded: "Clearly, contamination occurred somewhere in the laboratory process. Precisely how and where this has occurred in the laboratory has not been able to be determined."
Yesterday the Law Institute of Victoria said it appeared the decision to charge Mr Gesah was premature and the case was a reminder that DNA evidence was not infallible.
Representing the Victorian Criminal Bar, barrister Ian Freckelton, SC, said an avenue for civil action for Mr Gesah might be open if negligence and substantial injustice could be proven.
Shadow attorney-general Andrew McIntosh said the DNA bungle was terribly sad for the Tapp family and an indictment on the Victorian Government.
A spokeswoman for Police Minister Bob Cameron said the Government would not comment on the specifics of the DNA bungle relating to the Tapp murder case.
She rejected criticism of the Government's funding of police forensic services, saying Mr Overland had made it clear yesterday that the DNA contamination was a result of human error and not a lack of resources.