A US court has reversed the murder conviction of a former Minneapolis police officer who fatally shot an Australian woman in 2017, saying the charge did not fit the circumstances of the case.

Mohamed Noor was convicted of third-degree murder and second-degree manslaughter in the death of Justine Ruszczyk Damond, a dual US-Australian citizen who called emergency services to report a possible sexual assault behind her home.

He was sentenced to 12-and-a-half-years on the murder count but was not sentenced for manslaughter.

The Minnesota Supreme Court ruling means that his murder conviction is overturned and the case will now go back to the district court, where he will be sentenced on the manslaughter count.

He has already served more than 28 months of his murder sentence.

If sentenced to the likely four years for manslaughter, he could be eligible for supervised release around the end of this year.

Caitlinrose Fisher, one of the lawyers who worked on Noor’s appeal, said she was grateful that the Minnesota Supreme Court had clarified what constituted third-degree murder, and said she hoped it would lead to greater equity and consistency in charging decisions.

“We’ve said from the beginning that this was a tragedy but it wasn’t a murder, and now the Supreme Court agrees and recognises that,” she said.

The ruling could give former Minneapolis officer Derek Chauvin grounds to contest his own third-degree murder conviction in George Floyd’s death in May 2020.

But that would not have much impact on Chauvin as he was also convicted of the more serious count of second-degree murder and is serving 22-and-a-half-years.

Experts say it is unlikely that Chauvin would be successful in appealing his second-degree murder conviction.

The ruling in Noor’s case was also closely watched for its possible impact on three other former Minneapolis officers awaiting trial in Floyd’s death.

Prosecutors had wanted to add charges of aiding and abetting third-degree murder against them, but that is unlikely to happen now.

The trio are due to go on trial in March on charges of aiding and abetting both second-degree murder and manslaughter.

State law has defined third-degree murder as “an act eminently dangerous to others and evincing a depraved mind, without regard for human life”.

A central dispute has been whether “dangerous to others” must be read as plural, or if the fatal act can be directed at a single, specific person.

Ms Fisher argued on appeal that the language required that a defendant’s actions be directed at more than one person, and that the law was meant for cases such as indiscriminate killings.

But prosecutors urged the Minnesota Supreme Court to uphold the third-degree murder conviction, saying that nearly all killings by officers were directed at a specific person.