A Waiheke Community Board member has been found guilty of assaulting a 14-year-old boy who wandered on to his property looking for a lost dog.

Nobilangelo Ceramalus hit the boy, who cannot be identified, on the head with a branch that was described as "two inches wide" and "two or three feet long" on the afternoon of May 25.

The boy and his friend had been walking two family dogs through a section of bush when one of the pets, a 3kg chihuahua dressed in a little jacket, ran away after hearing a noise.

The boys chased the dog and found themselves in Ceramalus' section, which is also surrounded in bush.

"I went to pick up [the dog] to leave because I knew it wasn't our property," the boy, who is now 15, told the court yesterday. "Mr Ceramalus walked out of the house. He yelled at us and asked us what we were doing on his property.

"I apologised and was trying to leave his property and he started waving [his arms] around saying 'get off my property'.

"I saw him pick up a stick and I started to walk faster and he whacked me on the head with a bit of wood."

After the impact, which left him with a lump on his head and needing to see a chiropractor for a sore neck and back, the boy stumbled backwards into a small tree while still clutching the chihuahua.

"I turned around and said 'you can't hit a child on the head with a stick'. He said 'it doesn't matter because it will never hold up in court'."

But, after a day-long hearing in the Auckland District Court yesterday, the charge did stick when Judge Greg Davis found Ceramalus guilty of assault.

Despite Ceramalus referring throughout the hearing to the teenagers as liars, who were trying to get revenge after being caught trespassing on his property, Judge Davis said he found both boys' evidence to be "credible, honest and sincere".

An attempt to sentence Ceramalus was delayed until September after he indicated he would be requesting a discharge without conviction.

Ceramalus said of the guilty verdict: "Two teenagers have been taught that you can lie in a court of law and get away with it."

Outside the court the boy's mother said there was no reason for the boys to lie and the family were elated at the verdict.

She said Ceramalus' suggestions that the boys were liars who were coached in their evidence by politically motivated parents were ridiculous, especially given she had voted for him in the local body elections.

Waiheke Community Board chairman Tony Sears said the board was meeting tomorrow night and he imagined Ceramalus' case would be discussed.

Given it was so close to the end of the board's term and that a sentence had not yet been delivered, Mr Sears said it was unlikely the board would be calling for his resignation. But it would accept it if he offered to go.