Cape Town - The defence's DNA expert in the trial of alleged axe murderer Henri van Breda, told the Western Cape High Court on Wednesday that there was not enough DNA in 40 samples taken from the crime scene to yield valid results.
Dr Antonel Olckers faced her third day of gruelling cross-examination in the trial of 22-year-old Van Breda, who is accused of the axe murders of his parents and brother, and the attempted murder of his sister at their home in a security estate in Stellenbosch in January 2015.
Olckers told the court that "one cannot make a valid conclusion from an invalid interpretation" and this was the case in 40 samples, which she said did not have the minimal amount of 1 nano-gram of DNA evidence needed for a reliable result.
Of the 216 samples collected, Olckers received and analysed the data of 151 samples.
Earlier in the trial, state witness and chief forensic analyst Lieutenant-Colonel Sharlene Otto told the court that "no unknown DNA" had been found on the crime scene. She also told the court that the police forensic laboratory had had no problem finding DNA in any of the samples.
But, Olckers told the court that where there is not enough DNA, as in the case of 40 samples she identified, "whatever profile you get is invalid. Its wrong, its invalid and it should not be used".
She said no female profile could be read into a DNA sample found in the shower. This was contrary to Otto's evidence that a mixture of DNA profiles of brothers Rudi and Henri and the mother Teresa were found.
Olckers said the "process in some samples was followed through to the end when the process should have stopped earlier as it was invalid".
Senior state prosecutor Susan Galloway said that to "prevent the guilty from going free and the innocent from going to jail" one would expect the Forensic Science Laboratory to go further than that. She referred to Otto's testimony that 0,05 nano-grams of DNA evidence is needed for a reliable result.
"You want the court to make a finding that these 40 samples must be ignored yet you take those flawed results and make calculations from them", Galloway said.
Olckers insisted that Otto had used "only the qualitative data and not the quantitative data". If she had worked in the Forensic Science Laboratory herself, she would have stopped the process, she told the court.
She said Otto had "remained silent" on foreign peaks found in a sample, but they could be an indication of the presence of a low level profile.
But, Galloway countered that Otto had not testified about the foreign peaks as they were of "no consequence" and accused Olckers of manipulating the data.
Galloway told the court the foreign peaks could have been from two domestic workers or from the first respondents.
Olckers conceded that the peaks could not be explained: "I can't categorically say if its an allele or part of a profile". (At least nine alleles are needed for scientists to extract a DNA profile).
Van Breda has claimed that an intruder, armed with an axe and knife, wearing dark clothing, a balaclava and gloves, was behind the murders.
In his plea explanation he said he also recalled “hearing what sounded like angry voices of more than one person, somewhere else in the house. Although I could not distinguish specific words, it sounded like the persons were speaking Afrikaans”.
He has pleaded not guilty to all the charges against him.
The trial continues.