Wellington, Nov 8 NZPA - Police say that are looking into an alleged threat to kill an identical twin after a woman was yesterday convicted of killing the other twin.

Kathleen O'Sullivan, 44, pleaded guilty in the High Court in Wellington to the manslaughter of James Brown, averting a murder trial that was to start on Monday, The Dominion Post reported.

The Crown said she hit James Brown, 48, with a softball bat at least twice at a house in Lower Hutt on October 25 last year, damaging his spleen. He died nine days later in hospital, aged 48.

Mr Brown's identical twin John was in the public gallery with his brother's ashes in a small casket -- to see O'Sullivan face justice.

Police confirmed they were investigating O'Sullivan's sister, Noreen for allegedly telling John Brown after the hearing: "One down, one to go."

Noreen was the dead twin's former partner.

Detective Senior Sergeant Darrin Thomson confirmed that police were "actively investigating that comment".

O'Sullivan was remanded in custody for sentencing next month.

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