He was wearing boxer shorts and sandals as he entered the dock on Monday and asked magistrate Greg Jacobs for a French interpreter as his English was not good enough to listen to the case against him.
It is understood he was arrested at his cleaning job in Voortrekker Road.
Investigating officer detective WO Shaun Bardien told the court that Onyoka needed to be taken for blood tests in order to compare his DNA with evidence found at the murder scene.
Curran was reportedly found in a pool of blood by his girlfriend with only his cellphone missing.
Mellon Educate said in a media statement that Curran had just completed his contract as director of education in South Africa and that he was staying on for “a number of weeks” on vacation.
The organisation’s CEO Niall Mellon said they were assisting his family and expressed gratitude to people who had sent “warm wishes” and “empathy”.
“I know our many volunteers and supporters will be very sad to hear this tragic news. John was much loved by everyone who met him and especially by the thousands of children he helped during his time with Mellon Educate,” said Mellon.
The accused is expected to make a formal bail application on December 3.