Amber-Rose Rush's killer appeals, says Crown's key witness was the murderer

The Dunedin doctor who murdered teenager Amber-Rose Rush after she threatened him with sexual assault allegations is again accusing the Crown's key witness of being the killer.

Amber-Rose Rush, 16, was found dead in a pool of blood in her bedroom in Corstorphine in southwest Dunedin in early February, 2018.

Venod Skantha, 32, was charged with her murder, and found guilty by a jury in the High Court at Dunedin in November last year. He was also found guilty on four counts of threatening to kill.

He was later sentenced to life imprisonment with a minimum non-parole period of 19 years.

Part of Skantha's defence at trial was that a teenage friend who drove him to Rush's house - and later helped police catch Skantha - was the actual killer, who carried out the murder out of a misplaced sense of loyalty.

In the Court of Appeal in Wellington today, Skantha's lawyer Jonathan Eaton QC again pointed to the teenager as being the murderer, saying Skantha had no knowledge of the killing.

The murder happened in early February 2018 when Amber-Rose made a post on Instagram accusing Skantha of supplying alcohol to minors and "touching up young girls".

She said she would approach police and hospital bosses with the allegations.

At that point, Skantha had already been given a final warning for misconduct.

She and Skantha got into a heated argument over Facebook messenger, following which he put on dark clothes and had the teenage friend drive him to Amber-Rose's home in Clermiston Ave.

When he emerged from the house, he was carrying the victim's phone, licence, and a blood-soaked knife.

He told his friend to clean the car and other items, but an investigation uncovered Amber-Rose's DNA in the doctor's BMW and on his shoes.

Despite Skantha making death threats against him, the friend told police what happened and showed them where to find the evidence.

In court today, Eaton said they were appealing on the basis there was a miscarriage of justice which created "a real risk that the trial outcome was affected".

Eaton said there were "really unusual features of this case" that were "quite possibly verging on novel".

The first point related to the teenage driver.

"[He] was somebody who undoubtedly had extensive and detailed knowledge of the homicide which would either, if his evidence was reliable, make him an offender or somebody who the offender's spoken to."

The teenager, who has name suppression, had described himself as a compulsive liar, Eaton said.

Venod Skantha was found guilty by a jury of Amber-Rose's murder.

But police and the Crown "refused" to treat the witness as a suspect in the case.

Eaton said the teenager was the one who alerted Skantha to the Instagram post.

He pointed to "inconsistencies" and "peculiar" behaviour from the witness in his evidential interviews and during cross-examination at trial.

"It was no question that everybody could see his evidence had problems, the issue was why is that happening?

"An objective assessment as to why it's happening must recognise the risk that he is the offender who is looking to falsely implicate [Skantha]."

He said the witness had admitted he was a compulsive liar and had been exposed for "endless lies he can't explain", but the trial judge would not entertain the possibility he was the killer.

Eaton also advanced the appeal on the basis some of the evidence used at trial should never had been admissible.

He said propensity evidence where another witness claimed Skantha had committed indecent assault was allowed to be used in trial, but that the judge's direction mid-trial was that the jury must be sure it was an indecent assault and that it was operating on Skantha's mind on the night of February 2, when Amber-Rose was killed.

But at the end of the trial when the judge summed up the case, he did not refer to the indecent assault operating on Skantha's mind.

"All the directions he'd given in the trial are gone ... the direction changed, and I still don't know why it changed."

What the judge did say in summing up referred to whether Skantha was "mindful" of the allegations and would he be "concerned" about them.

But Eaton said the threshold was not meant to be "concern".

"It is far higher than that."

Crown lawyer Robin Bates said the Crown case never relied fully on the teenage witness' evidence - there was also a collection of pieces of circumstantial evidence.

He pointed to numerous pieces of evidence, including that the initial wound inflicted on Amber-Rose was a deep cut that severed two important blood vessels and her windpipe.

"The person who did that had some knowledge of what was required to immediately silence Amber-Rose Rush and kill her quickly," he said.

Eaton argued against that, saying there was no evidence from the pathologist at trial that the killer necessarily needed special knowledge.

Bates pointed to other pieces of evidence, including that the house Amber-Rose lived in was small and it would have been high risk for someone to enter it in the middle of the night to carry out the crime - and that whoever had done so must have had "a compelling reason" to go into the house.

Eaton said the teenage witness had been to Amber-Rose's house on multiple occasions and would be better placed to pass off his presence in the house than Skantha would have been.

Bates also said it was incorrect to write off all of the witness' evidence as unreliable.

His co-counsel, Richard Smith, addressed the issue around the propensity evidence, saying the judge did caution the jury not to use the evidence unfairly against Skantha.

He said the judge used the words "mindful" and "fearful", which were sufficient in explaining the context of whether Skantha was thinking about the threat to his career on the night of the murder.

The judges have reserved their decision.