The alleged attack at the couple's Merriwa home caused a life-threatening subdural haematoma - bleeding on the brain, which has left Rebecca Radnidge with lasting disabilities.

The case against Mr Riley was summed up in Newcastle District Court on Wednesday where he has pleaded not guilty to inflicting grievous bodily harm with intent, and an alternative count of recklessly cause grievous bodily harm.

In the triple 0 call he made on the night of December 5, 2019, played to the jury, Mr Riley tells the operator that his girlfriend was having a seizure and "I think she is dying, I don't know".

They'd had an argument earlier that night about a phonecall from Miss Radnidge to her mother about Christmas. The case turns on what happened next.

"We were fighting and it got a bit crazy and she started throwing up ... and then she went into a seizure," Mr Riley said on the call.

"We had a bit of a violent altercation and she may have hit her head ... it may have happened while she was biting my face ... all I care about is what is going on with her right now."

Defence Barrister Nicholas Moir said Mr Riley's version of events involves self defence.

Mr Riley says he was trying to leave the house but Miss Radnidge wouldn't let him. He tried to calm her down by cuddling her, but she bit him on the face. He slapped or pushed her to get her off and she landed on the couch, and at that point she became ill and started fitting.

"If someone was biting someone's face, for him to violently push her away I would have thought was just expected," Mr Moir told the jury.

There were inconsistencies in Miss Radnidge's evidence, he said, and reason to reject what she said on the grounds of credibility.

But Crown Prosecutor David Phillips said the nature and number of her injuries was not consistent with a single blow.

There was bruising to her right arm, consistent with her protecting herself from repeated blows to the head, he said.

And the medical evidence about a life-threatening subdural haematoma was consistent with a significant blow or blows - not a slap, he said. There was also evidence from her mother that he was bullying and controlling, he said.

"Do you really accept what he's said, that he wasn't able to leave the house, given his size and strength," Mr Phillips said.

"The fact he was acting in rage is not a defence."

What he did was in not in proportion, Mr Phillips told the jury, and even if it was necessary, what he went on to do was not reasonable.

The accused also gave different versions of events, the first involving a knife which was not mentioned in later interviews with police, Mr Phillips said.

Judge Donna Woodburne is expected to sum up on Thursday before sending the jury out to begin their deliberations.

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