(Feb. 11) -- A Hong Kong court today overturned the verdict in what became known as the "milkshake murder" involving an American woman who admitted killing her husband by spiking his drink with a date-rape drug and clubbing him with a brass ornament.

Nancy Kissel, 46, of Adrian, Mich., had always claimed that she was a victim of years of domestic violence and had acted in self-defense in 2003 during an argument about divorce with her husband, Robert, a wealthy investment banker.

Today the Court of Final Appeal said prosecutors had used prejudicial evidence in the original trial in 2005 and that Kissel's motive needed re-examination. It ordered a new trial, but ruled that Kissel must remain in custody.

AFP / Getty Images
Nancy Kissel, here in court in 2005, admitted killing her husband, but said she was acting in self-defense during an argument with him about divorce.
Kissel arrived in court in a wheelchair and broke into tears after the finding. Her first appeal against a life sentence, in 2008, was denied, a decision that was roundly criticized by the highest court's five justices.

The lower court's finding was "a departure from accepted norms so serious as to constitute a substantial and grave injustice for which her conviction should be quashed,'' Justice Kemal Bokhary said.

"Mrs. Kissel killed Mr. Kissel," the judges found, according to a Reuters report. "But was the killing certainly murder or might it have been in self-defense?"

The killing became a sensation among Hong Kong's high-style expatriate community after Kissel claimed she had been forced to have anal and oral sex and that her husband committed adultery and used cocaine.

Prosecutors claimed that Kissel stood to inherit $18 million in insurance payouts and investments after the death of her husband, from Saddle River, N.J.

At the time of the killing, Kissel said, her husband had threatened her with a baseball bat, and she said she had given him the laced strawberry milkshake to calm him rather than as part of a plan to kill him. She pleaded not guilty to murder, a charge that requires premeditation.

The body was found four days later, wrapped in a carpet.

Justice Bokhary said "it is clear" Kissel had tried to conceal the body, but questioned whether it was to hide a murder or was an act of panic after a killing in self-defense, The New York Times reported.