A Sydney court is now determining who knew what and when they knew it, as Houston's lawyer argues he had a reasonable excuse for not alerting authorities after his father's confession in late 1999 before his death in 2004.

Houston, 68, has pleaded not guilty to concealing a serious indictable offence of another person relating to his father.

The charge stems from the Royal Commission into Institutional Responses to Child Sexual Abuse which delivered its final report in 2017.

Houston founded the Hills Christian Life Centre in 1983, later merging with the Sydney branch founded by his father to become Hillsong.

It grew into a global megachurch. Its associated music group has won awards and major label contracts. Sermons were, until recently, broadcast on free-to-air television.

Before any of that, New Zealand-born Frank Houston was an up-and-coming pastor leading a Christian revival when he came to Australia, Brett Sengstock, the survivor of the pedophile pastor's abuse said.

In a January 1970 visit, the night before his eighth birthday, Frank Houston sexually abused Mr Sengstock for the first time, while staying in his family home.

He told his now-deceased mother about the abuse he suffered as a child later that decade.

The pair were on their way home from a counselling session she suggested he attend, with his abuser, who performed a sex act under a table during the meeting.

Mr Sengstock was "deeply ashamed" when she told him to stay quiet about it.

He felt under moral and spiritual control, and couldn't bring himself to say anything.

"It was very complicated to me," Mr Sengstock told Sydney's Downing Centre Local Court this week.

"My friends, my family and our family's family were all connected to the church."

Shortly before he told his mother, Mr Sengstock's great-aunt Barbara Taylor became the pastor at Emmanuel Christian Family Church Plumpton in western Sydney after her husband died in May 1977.

Decades later, Ms Taylor's niece told her Frank Houston abused her son, swearing her to secrecy.

Her niece told her the pastor "crept into his room and behaved inappropriately".

Ms Taylor did not know the exact form of the abuse until recently, having never asked.

"Quite frankly, I wasn't interested in all the yucky details," she told the court.

While Ms Taylor said she would no longer keep such a secret, she kept silent in the late 1990s, until Mr Sengstock's mother told someone else.

People were being "specifically challenged to give their lives to Jesus Christ" by an evangelist leading a "tent crusade" on the grounds of Ms Taylor's church.

"People were sharing their testimony of how abuse had messed up their lives. She felt she had to tell the evangelist," Ms Taylor said.

The evangelist, Kevin Mudford, would later show up at Mr Sengstock's home.

Mr Sengstock and Ms Taylor present somewhat differing accounts of what happened next.

He recalls the former bikie some called "Mad Dog Mudford" trying to force his way in, threatening Mr Sengstock and, along with Ms Taylor, telling him to let the church handle it.

Mr Mudford has not given evidence at the hearing, which is scheduled to continue until December 22.

Ms Taylor couldn't remember the words exchanged, only that Mr Sengstock was angry his mother had betrayed his confidence, and the "bombastic" Mr Mudford wanted to do something about it.

"It was the wrong thing to do for us to go there," she said.

But she did believe it was up to the church to handle.

"I believe judgment should begin at the house of God."

She told her grandnephew she would support him taking it to the church, but not the "secular courts".

Former pastor John McMartin "thought that was a very strange statement".

Ms Taylor and Mr Mudford came to him multiple times, beginning in 1998, frustrating him with a lack of information.

He later told the pair to tell Houston.

"Tell Brian," he told them. "He's higher up than me. Tell him."

Mr McMartin approached a national executive member of the Assemblies of God in Australia Pentecostal church network, who similarly told him to tell Houston.

"I've got some sad news, disturbing news," Mr McMartin recalled telling Houston in November 1999.

"Your father's been accused of misconduct with a minor," he told him.

Having known Houston for some time, even over the phone he could tell he was shocked.

Houston was also "shocked" when Hillsong's general manager George Aghajanian told him of the allegation the previous month at the end of one of their regularly scheduled meetings.

Mr Mudford had earlier that day accused the church of covering up the report of what Frank Houston had done, Mr Aghajanian said.

"There wasn't a cover-up. I received an allegation and I reported it to my boss (Houston)," Mr Aghajanian told the court.

Several witnesses have been given protection from prosecution in exchange for providing truthful evidence.

The case continues.

Australian Associated Press