The Supreme Court of Canada is hearing competing arguments over whether the so-called battered woman's defence should include the hiring of a hit man to kill an abusive spouse.

The high court is hearing the emotionally charged case of a Nova Scotia woman acquitted of counselling to commit murder after she tried to hire an undercover RCMP officer to kill her husband in 2008.

Nova Scotia prosecutor William Delaney argued that Nicole Ryan's particular circumstances don't entitle her to the Criminal Code's defences of duress and self-defence.

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The Nova Scotia Court of Appeal upheld her acquittal in 2010, concluding that Ms. Ryan's 15-year marriage amounted to a "reign of terror."

But Mr. Delaney argued that Ms. Ryan was not entitled to the legal defence of duress because she was not in imminent danger: she had moved in with relatives and was in the process of getting a divorce.

Mr. Delaney faced a grilling from some of the court's nine justices about whether the facts of Ms. Ryan's case could be adapted to fit the Criminal Code definition of self-defence, under which the battered woman's defence falls.

Ms. Ryan's lawyer Joel Pink said it was the accumulation of threats — a history of physical, sexual and mental abuse — that led Ms. Ryan to approach the undercover RCMP officer.

Mr. Pink said the Nova Scotia courts accepted Ms. Ryan's version's of the events of her marriage "in total."

He said Ms. Ryan called the police at least nine times and begged for protection for her and her daughter, but got none.

Even though Ms. Ryan and her husband had separated, her husband would turn up at the school of her daughter, prompting fears that he had plans to abduct her, said Mr. Pink.