Two people who separately told Brian Houston about allegations his father committed child sexual abuse have told a Sydney court he was "shocked" both times.
Hillsong's general manager George Aghajanian said he told Houston an allegation was circulating after an evangelist accused the church of covering it up in late October 1999.
"He had a shocked expression on his face," Mr Aghajanian said.
In November 1999, a pastor named John McMartin phoned Houston to tell him the same thing, with the Hillsong founder reacting with similar shock.
Then Houston asked him: "How do you know it's true?"
"I said, 'I don't know it's true but it has to be investigated'," Mr McMartin told a NSW court on Thursday.
Houston, 68, has pleaded not guilty to concealing a serious indictable offence of another person, relating to his father.
Mr Aghajanian told the court he believed he was the first person to tell Houston about reports of abuse committed by Frank Houston against Brett Sengstock, beginning in January 1970.
He told him at the end of one of their regularly scheduled meetings.
"I left that meeting thinking it was the first time he heard something about that," Mr Aghajanian said.
The court has heard Houston confronted his father about it in late 1999, who confessed, before his death in 2004.
Mr Aghajanian told the court the reports of abuse committed by Frank Houston were not reported to authorities because it was not a "current matter".
"Our understanding of our requirements was to report something that could be potentially an imminent danger," he said on Thursday.
The reported abuse was committed decades earlier and predated the church itself, he said.
Mr Sengstock has told the court he first told his mother about the abuse in the late 1970s, when he was a teenager.
Towards the late 1990s she told her aunt Barbara Taylor, also a church pastor, and then told an evangelist, Kevin Mudford, the court has heard.
Mr Mudford then accused the church of not acting upon the report in October 1999.
"He made the allegation we knew about this matter and were covering it up," Mr Aghajanian told the court, denying that allegation.
"There wasn't a cover up. I received an allegation and I reported it to my boss (Brian Houston)," he said.
"We had no evidence of Frank Houston offending in this manner prior to receiving that allegation."
A lack of evidence also prevented Mr McMartin reporting it when Mr Mudford and Ms Taylor came to him on multiple occasions, beginning in 1998, without any written complaint or identities.
"I was getting frustrated and said if you can't tell me the perpetrators name, tell Brian," he said.
"That was the attitude. 'He's higher up than me. Tell him,'" Mr McMartin recalled instructing the pair.
Houston's barrister Phillip Boulten SC has told the court his client had a reasonable excuse to not inform authorities, believing Mr Sengstock did not want further investigation.
Mr Sengstock disputed ever telling Houston that.
Mr Aghajanian said a letter to ordained ministers describing Frank Houston losing his church credentials would have been sent to at least 1100 people.
Houston also spoke about learning of his father's abuse at a 2002 Hillsong conference that would have had at least 18,000 in attendance, and was likely broadcast on television as well, Mr Aghajanian said.
The hearing in Sydney's Downing Centre Local Court is scheduled to continue until December 22, with Mr McMartin resuming evidence on Friday.
