Tristan James Kent pleaded not guilty to five charges related to the January 12 incident and took the matter to hearing in October.

In Wollongong Local Court on Monday, Magistrate Mark Douglass found Kent guilty of recklessly causing grievous bodily harm to his partner when he bit her, as well as possessing an unauthorised firearm.

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However, Magistrate Douglass found him not guilty of two counts of intentionally choking his girlfriend and assault occasioning actual bodily harm due to a lack of evidence.

The 29-year-old claimed he acted in self defence after the pair's drunken quarrel turned physical.

During the hearing, Kent denied he ever choked the then 19-year-old, as she alleged, and claimed she became verbally and physically abusive towards him and ignored his repeated requests for her to leave.

The court heard the couple had come home arguing after socialising with neighbours.

The woman claimed the fight was over Kent's bad joke; he alleges she had "smoked cones" all day and night and started "getting stuck into me".

Kent said he returned to the neighbours' house to escape the conflict but came back home after about 20 minutes because he could hear the woman screaming, crashing and cursing.

Kent said he took the woman's phone, telling her he would return it to her once she packed up and left.

He said she reached inside his pocket for his phone but, finding it empty - moved her hand to the front of his pants and grabbed him in an "extremely aggressive" way, "squeezing, pulling and twisting" his genitals.

As Kent was holding the woman from behind around the chest, she bit him on the arm prompting Kent to bite her on the ear.

Magistrate Douglass dismissed Kent's claims he was acting in self defence as he told the court during the hearing that "I bit her because she bit me" during the struggle over the phone.

"That is clearly not self defence," he said.

Magistrate Douglass also noted the woman had to receive medical treatment to her ear.

When determining whether Kent choked the woman, Magistrate Douglass said she was "not a good witness" and did not support her statement to police, with footage captured on the phone also not backing up her allegations.

"This was a good example of young people being way too intoxicated and not knowing how to deal with the issues in their relationship," he said.

Kent, who is in custody, will be sentenced on November 30.

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