"Proof of (Shadrock's) conviction for murder was a necessary element of the offence of being an accessory after the fact,'' said the ruling, released today.
It is understood the other co-accused also intend to appeal.
Mrs Wang died after being knocked down by a four-wheel drive in the carpark of the Manukau Westfield shopping centre in June 2008. She was chasing a bag snatcher
Police allege Shadrock snatched her bag and was driving the stolen four-wheel drive.
Mrs Wang later died in hospital from major head injuries.
Her 8-year-old son Edmund watched his mother being run down from the van she had been getting into when her bag was snatched. He was left alone while others rushed to where his mother lay bleeding.
Shadrock's retrial is scheduled for next June.