HONG KONG — An American expatriate convicted in Hong Kong of killing her investment banker husband after sedating him with a laced milkshake launched her final appeal of a life sentence on Tuesday.

Michigan native Nancy Kissel has been in jail since her conviction in September 2005. One appeals court has already upheld the ruling, but she is now seeking her last legal recourse in front of the Court of Final Appeal.

Kissel's lawyer Gerard McCoy argued that prosecutors improperly used information divulged at bail proceedings to support their case.

The defence argued at a bail hearing that Kissel was mentally fit to be released before her trial, but then Kissel claimed during the trial that she suffered memory loss after the killing, when she allegedly wrapped her husband's body in a rug and stashed it in a store room in the couple's luxury apartment complex.

McCoy said prosecutors violated Hong Kong criminal procedure when they cited the bail hearing to back their contention that Kissel was mentally sound at the time of the killing. He said Hong Kong laws bars such uses of material from bail hearings, so defendants can seek bail without fear of incriminating themselves.

Kissel, 45, attended Tuesday's hearing dressed in a dark suit jacket. She appeared frail, clutching the bars that enclosed the defendant's holding area when she stood as the justices entered the courtroom. She smiled at her supporters, who included her parents, relatives and a Catholic priest.

"She's weak. She can't walk very well. She needs a good medical work-up but she's got great spirits," Kissel's mother, Jean McGlothlin, told reporters. Kissel injured her knee in prison.

McGlothlin expressed optimism about the final appeal.

"I believe that we have the best group of people we could possibly have," she said.

Separated by metal bars, Kissel spoke to her father, Ira Keeshin, briefly after Tuesday's court session before she was returned to custody in a wheelchair.

"She's holding up quite well," Keeshin said.

Kissel's sensational trial made headlines worldwide with its allegations of drug abuse, kinky sex and adultery in the wealthy world of expatriates in this Asian financial hub.

Kissel admitted bashing her husband, Robert, in the head in self-defence as he was threatening her with a baseball bat in a quarrel. She described the 40-year-old investment banker for Merrill Lynch as an erratic, whiskey-swilling workaholic who also snorted cocaine and forced her to have painful anal sex.

Kissel was born in Adrian, Michigan, but her family had also lived in Minneapolis.