To shoot dead one's own children was the most gruesome thing anyone could do, Charlotte van der Westhuizen, mother of two of the three children shot dead by their own father, told the Cape High Court on Thursday.

She was called back to the witness stand for further cross-examination, after she had already endured six days of intense questioning by defence attorney, Milton de la Harpe.

On trial for the triple slaying before Judge Willem Louw and assessor M Powell is the father of the three children, senior police officer Marius van der Westhuizen.

It is alleged that he shot dead the children to punish his wife, also a police officer, for choosing her work above him and the home.

After Thursday's proceedings had run for two hours, De la Harpe told the court he had further aspects to cover but that they were very sensitive and personal to the wife and that he wished to do so "in camera", with the media excluded.

Only officials involved in the case were permitted to remain.

The wife recalled the night of the shooting itself, which happened after she had been caught out lying to her husband.

On the night in question, she had had to work until 6pm, instead of leaving work at 4.30pm.

Van der Westhuizen had "a thing" about his wife working so much overtime, instead of being at home to be a wife and mother.

Because of this, she had lied to him on the night of the slaying, saying she had been on her way home but had had to return to the Kuils River police station where she worked to fetch milk that she had left behind.

She told the court she had lied because she knew that Van der Westhuizen would be very angry if he knew she had once again worked late.

However, during the course of the evening, Van der Westhuizen had checked the car's mileage reading, and by so doing he had calculated that she had not returned to the office to fetch anything.

She said he confronted her about it, and she admitted she had lied and explained why.

Van der Westhuizen had then given her an ultimatum - she had to choose between him or her work.

When she said she could not make such a choice, as she had her work to do, as well as a husband and home, he took that to mean she had chosen her work above him, she told the court.

To punish her, he then took a firearm and shot the children dead in her presence one by one.

The case continues.

Sapa