You can't have it both ways‚ prosecutor tells Van Breda's DNA expert
Henri van Breda’s defence team was accused on Wednesday of “manipulating unclear data” in the triple axe murder trial.
Their DNA expert‚ Dr Antonel Olckers‚ was asked by the state why she had introduced a “foreign peak” found in the data when it carried no meaning.
Olckers said the peak on the line graph was “unexplained” and should have been raised by the state.
In DNA sequencing‚ an electropherogram plots results on a line graph. When a peak appears‚ it might be a useful contribution to building a full profile of a person‚ but far more data is required to suggest that someone’s DNA is present.
State prosecutor Susan Galloway told Olckers: “You were given black and white copies in low resolution‚ and you then manipulated what you had to get what you wanted from it.”
On Tuesday‚ Judge Siraj Desai raised the issue of Olckers scouring through piles of documents “merely to poke holes in the state’s defence” rather than doing an “independent analysis” which could inform her expert opinion.
He began Wednesday’s proceedings by asking Olckers to respond to cross-examination only with “pertinent” information.
This came after the most laborious day in the trial on Tuesday‚ with Olckers persistently giving lengthy answers which raised the ire of an exasperated Galloway.
On Wednesday‚ Galloway also accused Olckers of contradicting herself by criticising the state for analysing DNA samples which she said were below the optimum amount but then analysing the same samples herself to contradict the state’s findings.
“I compiled a list of samples I thought should not have progressed through the analysis system as they did at the state laboratory‚” said Olckers‚ “because they were below 1 nanogram.”
On this list were samples from the shower at the family home in Stellenbosch‚ where Van Breda is accused of murdering his parents and elder brother in January 2015.
Police DNA expert Lieutenant-Colonel Sharlene Otto said the samples came from Teresa van Breda and her two sons‚ Henri and Rudi‚ or possibly just the two sons.
According to Olckers‚ there was no female DNA in the samples‚ but Galloway said this was a strange conclusion when she had said the samples were too small to analyse at all.
“I am trying to point out to the court that they should not have gone through the system‚” responded Olckers.
Desai pressed Olckers for her expert opinion as a scientist‚ but instead she quoted from the standard operating procedures.
“Should evidence be ignored altogether if it is below 1 nanogram?” asked Desai.
Olckers said that “however much one would want to use a conclusion‚ if it is not based on valid data‚ the interpretation isn't valid and thus neither is the conclusion. That is how science works.”
Desai asked: “If it leads to a result with some degree of certainty should it then just be ignored?”
When Olckers said yes‚ Desai said she could be “proposing an unrealistic standard for the 21st century”.
When Olckers complained that one woman on the scene during evidence collection had not been in protective shoes‚ which was against standard operating procedures‚ Desai asked her: “To what extent would that compromise the results?”
Olckers replied: “I can only say the SOP wasn’t covered but I can’t calculate the effect of that.”
Desai said: “I am not asking you to calculate anything. I was asking for your expert opinion.”