PHNOM PENH, Cambodia — An Australian filmmaker charged with endangering Cambodia's national security told a judge Tuesday that his relationship with the now-disbanded opposition Cambodia National Rescue Party was purely professional.

James Ricketson, 69, was arrested in June last year for flying a camera-equipped drone over a rally held by the opposition party. The charge against him is tantamount in legal terms to espionage and is punishable by up to 10 years in prison.

Closing arguments in the trial are expected Wednesday. The judge questioned Ricketson on Tuesday about his relationship with the Cambodia National Rescue Party and the purpose and funding for his filmmaking. Ricketson has been painted by prosecutors as sympathetic to the opposition party.

The testimony of Ricketson and his witnesses has focused on establishing his credentials as a professional filmmaker and his charitable work in Cambodia. There has been virtually no evidence or testimony concerning his alleged crime to rebut.

Ricketson said he exchanged emails with opposition figure Sam Rainsy as part of his work and had planned to make a documentary about him, but that was their only connection. He also said he thought his documentary filmmaking could ultimately benefit Cambodia's poor people.

Two witnesses for Ricketson gave their accounts Tuesday of how he provided them with financial aid to help lift them out of poverty. The court previously heard similar testimony from a woman whose education and business as a street vendor he had financed.

Ricketson was arrested after he used a drone to film the final rally of the Cambodia National Rescue Party before last year's local elections. The party has since been dissolved as part of a sweeping crackdown on the opposition and media critical of Prime Minister Hun Sen's government. Ricketson's arrest was seen as a part of the crackdown, to intimidate journalists covering political developments.

The crackdown was widely viewed as an effort to ensure victory by Hun Sen's ruling party in last month's general election, in which it won all 125 seats in the National Assembly. With Hun Sen's extension of power accomplished, there has been speculation the courts — widely seen as under government control — might allow Ricketson to walk free. The government since the beginning of last week has released more than 20 political prisoners with pardons or bail.