For more than two decades Helen McMaugh kept dark memories of a sexual assault she endured as a teenager buried deep inside.

Key points: David Benedict Hogg, 65, has been convicted for sexual assault of a teenager in 1988. He is yet to be sentenced

David Benedict Hogg, 65, has been convicted for sexual assault of a teenager in 1988. He is yet to be sentenced Victim Helen McMaugh says he betrayed her trust

Victim Helen McMaugh says he betrayed her trust She says the assault was "covered up by the church and by the school"

That was until she saw her perpetrator being lauded in a major newspaper.

The man was David Benedict Hogg and he was being awarded for his work as the founder of the non-for-profit organisation Lifestyle Solutions.

The multi-million-dollar charity cares for 1,200 adults with disabilities and 300 foster children in group homes across the country.

"I was absolutely horrified," Ms McMaugh said.

She thought authorities knew about the former Baptist youth minister's past.

Hogg was banned from Ms McMaugh's high school in 1988 when the principal discovered Hogg had sexually assaulted Ms McMaugh while she was doing work experience with him.

In 2010, when Hogg appeared in the media, Ms McMaugh began making calls.

"That was when I found out that nothing has been done. It had just been covered up by everyone, by the church and by the school," she said.

Hogg, now aged 65, has been convicted of sexually assaulting her while she was a student at Carlingford High School, in Sydney's north-west.

During the trial the court heard Hogg had acknowledged he took the schoolgirl on a Friday night drive to counsel her, but he denied he took her to the Harbour Bridge and denied touching her at all.

His defence argued he was watching football at the house of another girl's family.

David Hogg, pictured in 2015, said the case has had "a great emotional affect" on him. ( AAP: Kylie Shaw )

At a sentencing hearing on Thursday, Hogg continued to maintain his innocence and said he "absolutely" did not sexually assault Ms McMaugh, but accepted he had been found guilty.

He said he'd been medicated for depression since he was charged, and had become embarrassed and paranoid when going out in public.

"I think it's had a great emotional and psychological effect [on me]," he said.

The court heard that since charges were laid, Hogg had lost his position on a number of community and not-for-profit boards, and was last week expelled from the board of Lifestyle Solutions following his conviction.

He was also affected by extensive media coverage of his case, which he "did not think was necessary".

"I feel embarrassed and ashamed by the coverage and how that was associated with me," he said.

Hogg's sentencing hearing will continue in May.

Victim speaks publicly for the first time

As a victim of sexual assault Ms McMaugh has a right to anonymity through the court process.

But with Hogg's conviction she's waived that right to speak publicly for the first time about what took place.

Now aged 45, she told the ABC how Hogg used the guise of counselling to betray her trust.

"I couldn't believe that [he'd] been pretending to try and help me and all he wanted was to molest me, it was really damaging," she said.

Ms McMaugh's assault came a short time after she transferred to Carlingford High, in time for Year 11 work experience.

The then 16-year-old had arranged to shadow Hogg, the school's former chaplain, as he did his work for NSW Family and Community Services.

For her Year 11 work experience, Ms McMaugh arranged to shadow Hogg as he did his work for NSW Family and Community Services. ( Supplied )

As a Baptist youth minister his work involved supporting juvenile offenders through the courts and working with homeless people.

As the week was drawing to a close, Hogg — then a married father-of-three — said he had one more job to do and drove the pair to a then-secluded carpark under the south-east pylon of the Sydney Harbour Bridge.

Hogg, who was then aged 35, encouraged the teenager to confide in him.

The court heard that just as she was at her most vulnerable, Hogg launched himself at the schoolgirl, kissing her and pulling her jeans down, and digitally penetrating her.

"I was completely frozen I just did not know what to do," Ms McMaugh said. "I couldn't speak, it was like I was talking underwater."

In a statement tendered the court Hogg then allegedly told her she was "very mature for your age", and "it's not my fault. I can't help being attracted to you".

In her statement to police Ms McMaugh said she told Hogg he should talk to his wife and convinced him to drive her home.

As she got out of his car, Hogg asked Ms McMaugh for a kiss to show that "everything is okay between us".

Hogg later banned from school

With the work experience over, Ms McMaugh thought her ordeal was over. But Hogg turned up at the school the following week.

The court heard Hogg bailed her up against a wall and insisted he had done nothing wrong.

"I was horrified. It made me feel like the school was his domain, it made me feel like I wasn't safe," Ms McMaugh said.

In her next class she was visibly upset when she confided in her friend Jamie Parker, who is now a Greens MP in NSW.

"It was a big shock for a young person to hear that," Mr Parker, who was a witness at the trial, said.

Jamie Parker, who's a Greens MP in NSW, said his friend had shown incredible bravery. ( AAP: Joel Carrett, file photo )

"Really vividly I remember feeling like I wanted to put my arms around her and kind of console her, but it didn't quite feel like I could do that.

"She was obviously incredibly distressed so it's one of those things that stays with you."

Mr Parker said he told his mother, who reported it to Principal Alan Beggs.

The court heard Mr Beggs, now deceased, told Ms McMaugh he would look into the matter and later said Hogg had been banned from the school.

Evidence tendered to the court showed the school principal wrote to the local chapter of the Baptist church. But, because Hogg had moved to a new area, nothing further was done.

Hogg went on to have a successful career with Mission Australia where he was allowed to continue to work with vulnerable people before setting up Lifestyle Solutions.

'I felt completely hopeless about my situation'

Like so many in a similar situation, shortly after her assault Ms McMaugh said she left home and dropped out of school.

She turned to drugs for a short while before re-establishing a life in Queensland.

"Within months I was suicidal and felt completely hopeless about my situation," she told the court in a victim impact statement.

"I had lost all trust in those who should have been there to help me."

"I couldn't believe that [he'd] been pretending to try and help me and all he wanted was to molest me," Ms McMaugh said. ( ABC News: Chris Taylor )

She said being betrayed by someone in authority has had a lasting impact on her life, both as a partner and a parent.

"I freeze whenever someone hugs me," she said.

"It also affected the way I raise my kids. I'm very protective of my two children to the extent where I didn't trust anyone."

But it's the impact of her assault on the charity and disability sector that has been the biggest surprise to Ms McMaugh.

Hogg was the founder of Lifestyle Solutions and its CEO for more than a decade before stepping down in mid 2016 due to the sexual assault investigation.

It was when police charged him with Ms McMaugh's assault that more whistleblowers about Hogg's non-profit organisation were empowered to come forward.

As the ABC revealed in 2017 there was a NSW ombudsman inquiry into practice failures relating to four deaths of people in its care, and a coronial inquiry into the prescription overdose death of a fifth person during Hogg's tenure.

The organisation was subject to a complaint on how it handled a sexual assault allegation in Queensland and lost its contracts in Victoria "over failures to address immediate client safety".

Victim's message to others: You don't need to hold secrets

Ms McMaugh said she hoped she had made a difference.

"I felt like I had given voice to my 16-year-old self during the trial," she said. "I'd like to think something good can come of this."

Mr Parker said his friend had shown incredible bravery.

"Helen's tenacity and her courage is something that should be applauded. It takes one person with the courage, with the bravery, and with the tenacity to stand up and say that, this is a perpetrator.

"Then it gives other people the confidence to come forward as well and take a stand."

Lifestyle Solutions has maintained it has new systems in place and is continuing to work with regulators on reforms.

Ms McMaugh said a key recommendation of the recent royal commission into clergy abuse was that police focus on "the credibility of the complaint or allegation rather than focusing only on the credibility of the complainant".

She hoped this applied to anyone else who, like her, was brave enough to come forward about any perpetrator.

"I strongly recommend anyone out there: please come forward. You don't need to hold the secret," she said.

"You don't need to hold the shame that comes with sexual molestation. The shame of that belongs with the perpetrator."

In the statement the NSW Baptist Church said Hogg had not been a minister in its church since 2007, and his accreditation was removed in 2010 because he was no longer serving in a ministry role and no longer attending a Baptist Church.

A spokesman said the Baptist network operated differently to other churches in that ministers "are not 'sent' from one church to another by a central hierarchy".

He said their historical files showed a letter was written by the Carlingford High School principal to the Carlingford Baptist Pastor indicating Hogg was not welcome at the school, but did not reference an allegation from a student, and at that time Hogg was no longer under that pastor's employ.

"If a letter like this was received by our office today, our Standards Unit would seek to understand further the concerns of the school and cooperate with them," the spokesman said.