Van Breda defence attempts to discredit forensic DNA analysis

SAMPLES of DNA found in Henri van Breda’s bathroom have not conclusively proven that there were three people in it.

Van Breda is accused of murdering his parents, Teresa and Martin, and his brother Rudi, as well as 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, in the Western Cape High Court yesterday.

Otto had been questioned about the DNA evidence and standard operating procedure.

She took the stand on Monday to give evidence on the DNA profiles of the Van Bredas, as well as the procedures involved when processing DNA evidence.

Yesterday, Combrink questioned Otto about the input of DNA to be analysed.

Otto said forensic analysts needed 0.005 nanograms 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 DNA profile.

“It’s dangerous working with too little DNA, and dangerous when working with too much, which is why there is a set amount,” she said this week.

Yesterday, she said that when assessing DNA samples analysts only looked at white blood cells, and that in forensics it was not about quantity but quality.

“The average forensic sample is not your optimal sample,” Otto said.

Combrink questioned the DNA evidence found in Henri’s bathroom shower.

Otto has said she couldn’t fully testify that what had been found was blood, but it was DNA.

On Monday, Otto said that three DNA profiles found in the corner of the shower belonged to Rudi, Henri and Teresa.

However, during cross-examination, Otto said that in instances of a mixed result – since Rudi and Henri share 50% of their DNA with Teresa – she could not unequivocally testify that the DNA belonged to two or three people.

Because three DNA profiles matched the sample that was tested, it did not mean the three people were necessarily in the bathroom.

The trial continues on Monday.