A former Knox Grammar teacher is threatening legal action against the child abuse royal commission over what he claims was his unlawful arrest on a warrant and evidence that, he believes, defamed him.

Christopher Fotis, who taught at the elite Sydney school in the 1980s, appeared before the Royal Commission into Institutional Responses to Child Sexual Abuse in April after being arrested on a warrant for failing to appear at an earlier date.

The commission heard in April that Mr Fotis had been suspected of being a balaclava-clad intruder who sexually assaulted a boy in his school dormitory bed in 1988.

Mr Fotis denied being the intruder and also told the court he had not known he was considered as a suspect until this year.

On Monday Mr Fotis' barrister, Margaret Bateman, told the commission her client was "pretty cranky" about what he believed was "unlawful behaviour from the commission".

"He has a number of claims against the commission and various commission staff for things like false imprisonment and unlawful arrest," Ms Bateman said.

Mr Fotis also believed he has been defamed by the commission in evidence it has received during hearings.

As the commission heard final submissions in its inquiry into events at Knox Grammar on Monday, it was revealed counsel assisting the commission, David Lloyd, had sought findings under the NSW Crimes Act against former Knox headmaster Ian Paterson.

The commission heard that Mr Lloyd argued Dr Paterson may have breached sections of the Act that related to hindering an investigation, concealing a serious indictable offence and perverting the course of justice.

Dr Paterson's lawyer, Jim Harrowell, told the commission Dr Paterson did not commit a crime by failing to give police information about alleged sexual assaults at the school.

Dr Paterson, the head of Knox Grammar from 1969 to 1998, told the commission in March he had not told everything he knew to an investigating police officer.

However, he later retreated from the admission and told the commission he had not misled police.

Mr Lloyd's submission has not yet been made public but Mr Harrowell told the commission: "The findings that are sought against Dr Paterson are findings in relation to three sections of the Crimes Act.

"If Dr Paterson did not tell or volunteer information, that is not a breach of section 315."

Mr Harrowell also said there was a "paucity of evidence" for any finding of concealing a serious offence in relation to Dr Paterson not telling police about the 1988 incident.

The commission also announced that Geoffrey Jackson, a member of the Jehovah's Witness church governing body in New York, has been summoned to appear on Friday as part of its inquiries into the church.

Mr Jackson is in Australia visiting family and the commission had previously been told he would not be able to give relevant information.