Hong Kong's top court yesterday quashed the conviction of American woman Nancy Kissel for drugging and bludgeoning her banker husband to death, one of the city's most sensational murder cases.

Mrs Kissel was dubbed the "milkshake murderer" and sentenced to life in prison in 2005 after being convicted of giving her high-flying husband, Robert, a sedatives-laced strawberry milkshake and then bludgeoning him to death in 2003.

"The court unanimously allows the appeal, quashes the conviction and orders a re-trial," Chief Justice Andrew Li said.

The 45-year-old's three-month trial featured a heady mix of adultery, violence, spying, greed and enormous wealth, gripping the former British colony and even inspiring books and films.

Grisly details emerged in the trial, including that Mrs Kissel rolled up her husband's body in a carpet and left it in the bedroom of their luxurious apartment for days before hiring workmen to carry it to a storeroom.

"Mrs Kissel killed Mr Kissel. That much is not in dispute. But was the killing certainly murder or might it have been in self defence?" the court said in its judgment.

The court said it was clear that Mrs Kissel concealed her husband's body after the killing.

"But is it certain that she did that to hide a murder? Or might it be that she panicked and tried to hide the fact of the killing even though it had been in self defence? The question is not whether a reasonable hypothetical jury that had sat through a fair trial free from any material irregularity and had been properly directed could, or even probably would, convict," the court said.

"It is whether such a jury would inevitably feel sure that Mrs Kissel was lying from start to finish and that she had planned and carried out a coldly calculated murder."

The judge ordered Mrs Kissel remanded in custody pending a bail hearing.

Simon Clarke, Kissel's lawyer, said that they were considering asking for a permanent stay of proceedings on the grounds that it would be impossible for Mrs Kissel to have a fair trial following media coverage of the case.

Mrs Kissel could walk free if the court granted the request.

The lawyer added that his client was "psychologically injured by the whole process" and had not decided whether to apply for bail before the re-trial.

Mrs Kissel, who wept both before and after the ruling, was "elated' her friends said.

Prosecutors had claimed Michigan-born Kissel stood to gain up to $18 million in insurance payouts from the death of her husband, a senior investment banker at Merrill Lynch.

The prosecution also argued that Mrs Kissel, a mother-of-three, wanted to take her husband's money and run away with a TV repairman with whom she admitted having an affair in the US.

Mrs Kissel admitted from the witness box that she killed her husband but claimed she was acting in self-defence after he attacked her with a baseball bat on the night of the murder.

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