The Supreme Court has quashed the conviction of a Christchurch man found guilty of punching his four-year-old son in the face and pulling his ear.
James Mason's conviction for the 2007 assault was regarded as the first test of a controversial childhood discipline law.
He was sentenced to nine months' supervision and ordered to go to an anger management course.
In October, Mr Mason took the case to New Zealand's highest court after losing an appeal in the Court of Appeal in May.
His lawyer argued he had suffered a miscarriage of justice, because the punch and the ear pulling were both included in the same charge.
In its decision released on Wednesday, the Supreme Court agreed with Mr Mason and quashed his conviction.
Justice Blanchard said the division of the charge into two separate counts was the only proper course because the two acts of assault were of a different character and seriousness.
There has been no order for a retrial.
Mr Mason says he is elated the court has quashed his conviction.