The manner in which former police officer Marius van der Westhuizen shot dead his three children one-by-one — waiting for their mother's presence in the room before shooting — showed that his actions were "goal directed and purposeful", the Cape High Court heard on Wednesday.

Van der Westhuizen is on trial before Judge Willem Louw and assessor M Powell on three charges of murder.

Forensic psychiatrist Larissa Panieri-Peter told the court the manner in which the three shootings occurred showed that there was "clear-thinking" on Van der Westhuizen's part.

Prosecutor Mornay Julius told Panieri-Peter there were three different versions of the shooting (one given by van der Westhuizen's wife, Charlotte, and the other two by defence attorney, Milton de la Harpe).

In the wife's version, Van der Westhuizen had given her an ultimatum to choose between himself or her work as a police captain.

Van der Westhuizen had perceived that his wife chose her work above him, and had told her: "You have made your choice, now you must take the consequences."

He had then removed a firearm from a locked safe, relocked the safe, and had then gone to the two bedrooms where the children, two girls and a boy, slept.

He had waited for his wife to enter the girl's room before saying to his wife, "you have made your choice", and shooting the older girl.

Van der Westhuizen had repeated these words before shooting dead the second girl, and had then gone to the boy's room.

In the boy's room, he had again waited for his wife to enter before repeating his words and shooting the boy dead as well.

Panieri-Peter said, Van der Westhuizen's unlocking of the safe, removing the gun and relocking the safe indicated a "predative mind", and was careful and deliberate behaviour.

Before entering the girl's room, Van der Westhuizen had taken his wife's cellphone to stop her calling for help.

Panieri-Peter said this showed his intent to do something, and that he did not want his wife to call for help.

She said the wife "had to pay and suffer for choosing her work above himself".

She added: "She had to face the consequences."

The case continues.

Sapa