Garry Mulroy, the former Trinity Catholic College schoolteacher facing pedophilia charges in Cambodia, has been sent back to prison after a court appearance in the capital, Phnom Penh, in which judges deferred their decision on whether the charges should be dropped.

Speaking to AAP outside the court on Friday, Mulroy asserted his innocence of all charges and said that what “irked” him was that the six boys in his care at an NGO he set up named Education House had lost their opportunity for an education “and for life in general”.

Cambodian police allege the 64-year-old schoolteacher had procured the boys for sex in exchange for food and money.

However, an independent report commissioned by the defence found no evidence to support the charges. Mulroy was a victim of an extortion bid amid petty rivalries among foreign-run charities, it said.

The report, by risk management consultant Ross Milosevic, which included affidavits from people who knew the children, also found that police interviews were made "under extreme duress, intimidation and extortion".

"I can honestly say these boys were never abused by the accused. The boys’ honesty and demeanour showed no attitude that they were ever mistreated or abused sexually in any way," one witness says in the report.

The Investigative Chambers of the Phnom Penh Appeals Court was to rule on two submissions on Friday: to annul the charges amid defence claims of a lack of police evidence, and on follow-up interviews with witnesses.

Mulroy's lawyer So Mosseny said the court would not rule on witness testimony because an investigative judge had not conducted all requested interviews.

He said the annulment hearing was postponed to a date to be determined.

A visibly disappointed Mulroy was returned to prison in Siem Reap in the northwest of the country.

A trial date for charges he sexually abused boys under the age of 15 has been set for March 24 in Siem Reap.