A woman dubbed the "Black Widow" for murdering her husband has had her Supreme Court appeal against her convictions rejected.
Helen Milner was found guilty last year of the 2009 murder of her husband, Philip Nisbet, by giving him an overdose of an antihistamine he was allergic to, motivated by a $250,000 life insurance payout. She was also found guilty of two charges of his earlier attempted murder.
She was sentenced to life in prison with a non-parole period of 17 years.
Mr Nisbet's death was initially treated as a suicide but the case was reopened in 2011 after an investigation by his sister, Lee-Anne Cartier, and an inquest.
Milner appealed against her conviction to the Court of Appeal last year, arguing the Crown had failed to prove how the poison got into Mr Nisbet's system.
However, the Court of Appeal rejected her argument, prompting her to appeal to the Supreme Court on the same basis.
It found in a ruling released today there was no basis for the appeal and rejected her application.