A crucial witness in a murder trial, accused by the defence of being the real killer, yesterday denied there was any arrangement to keep quiet about what she had supposedly done.

Suwapa Kampan was giving evidence in the High Court at Auckland against her former partner, Grant Elliott Wills, 57, with whom she has two children.

Wills is accused of beating to death Ms Kampan's new partner, Somwes Suksabai, 29, with a stone kitchen pestle and attempting to murder Ms Kampan, 37, or alternatively injuring her with intent to cause her grievous bodily harm.

The killing happened in March last year as the couple slept in the bedroom of their Henderson home, where Wills lived in a spare room.

Ms Kampan, who suffered a crushed finger and a cut head, told the jury she repeatedly asked Wills to phone the police and accept responsibility for what he had done.

Initially, he allegedly said he would rather die than return to prison, but eventually agreed to call the police, she said.

Ms Kampan has denied numerous accusations by defence lawyer Peter Winter that she was the real killer.

The defence contends that she suffered her injuries through a misdirected blow from the pestle she was wielding and in the fatal struggle with Mr Suksabai.

Mr Winter said Wills agreed to call the police but told Ms Kampan he would not make any statement to them about how, as the defence claims, Ms Kampan killed her new partner, even though it meant that the police would probably charge him with the murder.

Ms Kampan denied there was any agreement that Wills would not tell the police what she had supposedly done.

She denied agreeing that she and Wills would then see what happened.

The Crown says Wills intended taking the children to Thailand where he had made internet chat room contact with two women.

One of the women, Tanya Nuantip, told the jury she believed Wills intended going for a "long, long time".

Ms Kampan said she would never allow her children to go to Thailand.

- NZPA