Cape Town - DNA samples found in Henri van Breda’s bathroom did not conclusively prove that there had been three people there.
This emerged on day 31 of the Van Breda trial in which Henri van Breda is accused of murdering his parents, Teresa and Martin, and his brother, Rudi, and attempting to murder his sister Marli.
Defence advocate Matthys Combrink continued to lock horns with the chief forensic analyst at the police’s forensic laboratory, Lieutenant-Colonel Sharlene Otto, as she was intensely questioned about the DNA evidence and Standard Operating Procedure (SOPs) on Friday.
Otto took the witness stand in the Western Cape High Court on Monday to give evidence about the DNA profiles of the Van Breda family, and the procedures involved when processing DNA evidence. On Friday, Combrink continued interrogating the expert witness about the input of DNA to be analysed. Otto had testified that they needed 0.005nanograms per microlitre after qualification to be able to create a DNA profile.
Anything less and the machine they used would not be able to create a sufficient profile for the analyst.
“It’s dangerous working with too little DNA and dangerous when working with too much, which is why there is a set amount,” she explained earlier this week.
She added on Friday that when looking at DNA, analysts only look at white blood cells, and that in forensics it’s not about quantity but quality.
“The average forensic sample is not your optimal sample,” Otto said.
Chief forensic analyst Lieutenant-Colonel Sharlene Otto under cross-examination in the Van Breda trial in the Western Cape High Court. Picture: David Ritchie/ANA Pictures
Combrink interrogated the DNA evidence that was found in Henri’s bathroom shower. Otto had previously said that she couldn't fully state that this was blood, but it was DNA.
On Monday, she indicated the three DNA profiles found in the corner of the shower belonged to Rudi, Henri and their mother, Teresa. However, during cross-examination Otto revealed that in instances of a mixed result, since Rudi and Henri share 50% of their DNA with their mother, she couldn’t unequivocally state that the DNA belonged to only two or three people. Just because three profiles matched the sample that was tested, it didn’t mean that the three people were necessarily there.
Earlier in the week, State lawyer Susan Galloway had tried to ascertain if someone could enter an environment, and not leave evidence, to which defence advocate Pieter Botha objected, stating this was inviting the witness to speculate.
Galloway then allowed Otto to explain the “Locard principle” which states that “every touch leaves a trace”.
During cross-examination, Otto had said that if a perpetrator was wearing protective gear, it was possible for them to not leave a trace.
“If a person is wearing a balaclava and gloves, with normal clothes, I wouldn't expect them to leave DNA,” said Otto. She explained this was because the face and hands often shed a lot of DNA naturally.
Otto said in such instances the environment would leave a trace on the person wearing the protective gear.
The trial continues on Monday.