The mother of school boy Jacques Pretorius, who was killed by fellow pupil Morne Harmse with a samurai sword, broke down and wept at the High Court in Johannesburg on Monday.

"We are broken," she said, when asked during sentencing procedures on how the killing of her 16-year-old son had affected her family.

Dressed in a black shirt and pants, she shook uncontrollably and was in tears.

She said forgiveness was not possible. "I can't ever in my life forgive what he did to us."

During the testimony, Harmse's mother, also burst into tears.

"It was never in my heart to kill"

Earlier his defence lawyer Dolph Jonker read out a letter Harmse had written to the judge, Phillip Hattingh.

"I want to make it clear that it was never in my heart to harm or kill anyone. I will for the rest of my life, live with what happened."

Harmse also said he hoped the family of Pretorius would one day forgive him.

The case resumes on Tuesday morning.