OTTAWA, Ont. -- The Supreme Court of Canada revisits the battered woman's defence when it rules on Friday in the explosive and emotional case of a Nova Scotia woman who tried to hire a hit man to kill her abusive husband.

The widely anticipated ruling could reshape the landmark defence for abused women.

In 1990, Canada's top court set a precedent when it restored the acquittal of Manitoba's Angelique Lavallee on the grounds of self defence after she fatally shot her abusive boyfriend.

Almost a quarter century later, the high court is considering the case of 115-pound Nicole Ryan, whose marriage to a 230-pound ex-soldier was described as a "reign of terror" by the Nova Scotia trial judge who originally acquitted her of attempted murder.

An appeal court judge upheld Ryan's acquittal, but the Crown appealed to the Supreme Court.

Ryan called police at least nine times to seek protection from her husband, Michael, who repeatedly threatened her and her daughter.

Instead, the RCMP eventually arrested her in March 2008 after they sent an undercover officer to pose as the hit man that Ryan was trying to hire to kill her husband.

The couple had separated and moved apart, but Ryan became terrified for her daughter's safety when her father began showing up at her school.

Once, during their marriage, Michael Ryan took his wife and daughter to a remote, forested spot and told them this was where he planned to bury their bodies.

"(Nicole) Ryan's factual record is so strong," said University of Ottawa law professor Elizabeth Sheehy, a legal adviser for the interveners in the case and the author of an upcoming book on battered women who have killed.

"Her testimony detailing her former partner's violence and threats, as well as her ongoing fear and efforts to secure aid from 911 and police, was accepted without reservation by the judges. It shows that her actions were not voluntary in any meaningful sense and should not be punished."

Kim Pate, executive Director of the Canadian Association of Elizabeth Fry Societies, said it is time for the Supreme Court to close the legal gaps in the Criminal Code that leave battered women unprotected.

"At least in theory, we're supposed to have equal rights now," said Pate.

Ryan's case helps "draw bright lines between defences that battered women fall between and end up convicted when they do seek to protect themselves and their children. Surely we're not in a state where that's still seen as acceptable."

The legal issue in Ryan's case turns on the merits of two different criminal law defences that can allow an accused person to be acquitted of a crime -- that they acted in self-defence or that they were acting under duress.

Friday's ruling will have to clarify whether the battered woman's defence should be expanded to include duress -- Ryan's act of attempting to hire a hit man to kill an abusive spouse.

Pate said the police clearly entrapped Ryan, and that she should not be punished for them ignoring her pleas for protection.

"Horribly, when that protection was not forthcoming, she acted to try to protect herself. When she did that she was essentially entrapped by the same police who wouldn't assist her in the first place."

Sheehy said Friday's ruling will clarify "the boundaries of the amorphous common law defence of duress, which has been in a state of juridical limbo" since a 2001 decision.

"Whether or not her acquittal is upheld, I hope that the court will also accept that self-defence is available for women like Nicole Ryan who have planned self-defensive homicide in advance or turned to third parties for help."

Ryan's lawyer said Thursday that she is trying to get on with her life, and is keen to avoid the public spotlight.

"She back doing what she loves doing, which is teaching. She's trying to get on with her life," Halifax lawyer Joel Pink told The Canadian Press in an interview.

But even if she wins a resounding victory Friday, the Supreme Court will have no power to give Ryan what she was originally seeking when she tried to hire a hit man -- protection for her daughter.

"All I know is that the husband, with his girlfriend, took off with the daughter after the trial and before the decision," Pink said Thursday.

"If I remember correctly, we have not heard from her since."