An appeals court has found a woman who stabbed a man to death suffered a miscarriage of justice after a dispute over whether she told a friend "it felt so good" after the killing.
A jury found Lily Ridgeway guilty of manslaughter in 2022 for killing Jason Adams two years earlier near Newcastle, a charge she denied on the grounds the death was accidental or that she only acted in self-defence.
But the NSW Court of Criminal Appeal quashed that conviction earlier in May and ordered a retrial.
In a full judgment released on Friday, the court found her lawyer and the trial judge failed in letting the jury rely on evidence that Ridgeway allegedly told a friend "it felt so good" after the stabbing.
Nikita Hanson signed a police statement saying Ridgeway uttered the phrase very soon after Mr Adams was stabbed.
The incident happened outside Ms Hanson's home, where Mr Adams was required to live under his bail conditions until their relationship went downhill and he began sending her threatening messages.
But at trial, Ms Hanson said Ridgeway never uttered those words - despite admitting she earlier made the contradictory statement to police.
Ridgeway's lawyer did not object when the prosecution cited the "it felt so good" phrase in its closing, nor did the judge direct the jury to limit the weight they put on the claimed wording when reaching a verdict.
The appeals court found the evidence would have been inadmissible if an objection had been raised.
"Notwithstanding that failure, the trial judge nonetheless had an obligation to ensure the applicant had a fair trial, which required (them) to make enquiry of defence counsel to see if a direction should be given," the three appeal judges said.
"The failure of the trial judge to take any such step resulted in a miscarriage of justice."
Ridgeway, who was initially jailed for seven years and seven months, told police she blacked out and went into "survival mode" when she stabbed Mr Adams outside Ms Hanson's house.
She had previously been the victim of serious domestic assaults and the appeal court found it was not "glaringly improbable" that she had reacted instinctively when she saw what she claimed could have been a knife in Mr Adams' hand.
Ridgeway's trial lawyer told the appeal she had no forensic or tactical reason for failing to object to Ms Hanson's evidence, rather stating it was an oversight.
The appeal judges ruled the phrase "it felt so good" was "highly prejudicial evidence".
At trial, the jury asked two questions about using the phrase as part of their deliberations.
"It is plain from these questions that the jury were concerned about what use they could make of this evidence," the appeals court said.
"As is clear, the jury were not told that they were not permitted to rely upon the words 'it felt so good' to prove the applicant's state of mind at the time of the stabbing."
Ridgeway was granted bail before a scheduled retrial.
She is due back in the NSW Supreme Court on June 7 for her arraignment.
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