Sydney nurse killer Walter Marsh will die in jail after losing appeal

The former US marine who slit the throat of much-loved Sydney nurse Michelle Beets has lost his bid to overturn his conviction and life sentence.

Walter Marsh, 54, was sentenced to life imprisonment in 2012 for the murder of Ms Beets, 57, who he killed outside her Chatswood home in Sydney's north.

Marsh grabbed Ms Beets on April 27, 2010 and slit her throat in a technique he learnt when he was a marine. He then repeatedly stabbed and left her for dead.

Marsh launched an appeal of his sentence and conviction earlier this year, saying life was manifestly excessive because the crime did not apply to the "worst case" category.

But today the Court of Criminal Appeal disagreed, dismissing the appeal on both fronts.

Marsh's barrister, Winston Terracini SC, told his appeal hearing earlier this year that a video demonstrating how a sentry could be attacked from behind with a knife and then stabbed should never have been admitted into evidence at the trial as it was "incredibly prejudicial".

He argued an appropriate sentence would have been about 32 years.

But crown prosecutor Nanette Williams said Marsh's crime did fit into the worst case.

Marsh had shown an extraordinary level of brutality and preparation, including stalking Ms Beets and practising the sentry attack on his wife Samantha Marsh before the killing, she said.

Marsh, a US citizen who wanted permanent residency in Australia, worked as a nurse at Royal North Shore and believed Ms Beets was responsible for his inability to find another job and an obstacle to him getting residency.

Cheers and applause erupted in court when he was sentenced to life in 2012, with Justice Derek Price describing the murder as "cruel, merciless and abhorrent".

The last moments of Ms Beets' life must have been horrifying, he said.

Ms Beets' partner, David Grant, was in court to hear the outcome of the appeal.

Speaking outside court Mr Grant said he was relieved.

"It has been a tough time ... Every time this comes up it is pretty hard to deal with and emotional," he told reporters.