A strand of blonde hair was found in the palm of Marli van Breda's hand following the axe attacks on her family, the Western Cape High Court heard on Monday.
The blonde hair was between Marli's middle and ring finger, curled around her forefinger and lay across her palm and was similar to her brother Henri's hair, forensic analyst Lieutenant Colonel Henry Stuart told the court.
He explained that hair analysis was considered "associative evidence" in court, and was used to exclude or include someone, but not identify them. DNA testing could only be done if the root was attached to the strand.
Pieter Botha, for Henri van Breda, said the hair could not possibly be his client's. He referred to a photo taken of the then 20-year-old on the morning of the murders.
Van Breda has pleaded not guilty to charges of axing his parents Martin, 54, and Teresa, 55, and brother Rudi, 22, to death, attempting to murder Marli, and defeating the ends of justice.
He alleges an intruder armed with an axe and a knife attacked the family in their home in the De Zalze estate, Stellenbosch, in the early hours of January 27, 2015.
Botha said Van Breda's hair was at most 30mm in length.
"What are the chances of those hairs coming from the head of my client on that day?" he asked Stuart.
Chances are slim, the officer responded.
"The chances, with respect, are nil," Botha shot back, and Stuart conceded.
Botha said a pillow was taken from the bedroom in which Martin and Rudi's bodies were found and placed under Marli's head to help her breathe. A towel was used to cover the then 16-year-old, who had a severed jugular vein and severe head injuries.
Botha asked Stuart if hairs could have been transferred to her hand if she had grasped these items. Stuart responded that it could. The hair could also have fallen into her hand, he testified.
Botha referred to a report by one Dr Potgieter, who treated Marli at Stellenbosch Mediclinic. According to his statement, he took forensic samples of nail scrapings and cuttings. These were sealed in a kit and given to the investigating officer.
The hair strand was placed in a bag with a handwritten note. The warrant officer who handled forensics confirmed the nail scrapings and cuttings were received and didn't make reference to any hairs. He mentioned that both her hands were bloody.
Fourteen hair samples, including hair from the family, were sent for analysis.
Van Breda claimed the attacker was a black man and wore a balaclava, dark clothes, and gloves.
According to Stuart, hair of "African origin" was curly or kinked.
All of the hair collected at the scene was straight, and either red, blonde or black.
The trial continues.