A woman jailed over the murder of a retired schoolteacher whose body wasn't found in his NSW Blue Mountains home for a month, has had her conviction quashed.
But the NSW Court of Criminal Appeal on Monday ordered that Ammie Douglass face a retrial over the fatal stabbing said to have taken place with a co-offender during an intended theft.
The now 30-year-old was jailed last year for at least 19 years and six months after a NSW Supreme Court jury found her guilty of murdering Christopher Whiteley.
The 69-year-old's severely decomposed body was not found until a month after he was stabbed to death in his Lithgow home in August 2016.
"Mr Whiteley died an unnecessary, painful and lonely death which has caused considerable trauma to others," Justice Monika Schmidt said when setting a maximum term of 26 years.
The appeal court on Monday upheld Douglass's challenge to her conviction, finding the trial judge failed to leave an alternative verdict of manslaughter to the jury.
Her trial heard she and her co-offender - given the pseudonym "A" - went to Mr Whiteley's home for an intended theft and either both of them, or at least A, was armed with a knife.
The Crown had contended that Douglass stabbed Mr Whiteley in an act contributing to death, or she was part of an "extended joint criminal enterprise" which resulted in the death.
"A" was called by the Crown and gave evidence against Douglass and was given an undertaking he would receive a discount on his sentence.
The appeal court noted neither the Crown nor the defence had submitted that whatever occurred was manslaughter and not murder.
But it concluded that manslaughter was a "sufficiently viable" alternative verdict in the circumstances of the trial to have been left to the jury.
The matter is listed for arraignment in the Supreme Court on Friday.
