A jury was intimidated by angry family members of two dead young people to convict the man accused of their murders, according to his defence lawyer.
Darin Gardner was found guilty of the murders of Melissa Viall, 23, and Kane Wright, 19, after driving into a crowd in October 2006 and jailed for life with a non-parole period of 18 years.
But yesterday a trio of high-powered lawyers, Barry Hart, Greg King and Howard Lawry, argued for Gardner's convictions and sentence to be overturned by the Court of Appeal.
Gary Gotlieb, Mr Gardner's defence lawyer at trial, gave evidence at the hearing and said the jury was frightened by relatives of Miss Viall and Mr Wright as they walked into the courtroom on a number of occasions.
The experienced criminal barrister said he "had never seen anything like it" and Mr Hart, referring to Mr Gotlieb's evidence, said Mr Gardner did not get a fair trial because of the alleged interference.
Mr King, who has been in London fighting for John Barlow's double murder convictions to be quashed by the Privy Council, argued that the trial judge for Mr Gardner erred in law when summing up.
The Wellington barrister said that Justice Hugh Williams failed to direct the jury properly in the matter of provocation, arguing that the most experienced judge in New Zealand had "raised the bar" too high.
Mr King said this undermined the defence case, who were seeking manslaughter as a possible conviction for Mr Gardner.
Crown prosecutors Mathew Downs and Aaron Perkins rebutted the case for appeal, mainly on written submissions to the panel of three Court of Appeal judges, Justices Young, Arnold and Venning.
The Court of Appeal has reserved its decision.
Gardner, 26, twice drove into the crowd of partygoers outside a 21st birthday in the Auckland suburb of Pakuranga in October 2006 .
Miss Viall was killed while giving first aid to Mr Wright, who had been knocked down by the car.
Mr Wright died the next day.
Outside court yesterday, his mother Sharon Wright said the appeal process had been difficult for the family to handle, more than 12 months after Gardner was sentenced.
Mrs Wright rejected any suggestion that family and friends threatened members of the jury.
"We were told from day one not to say anything and we were controlled during that whole trial."
