"I can't stop the horrible memories playing over in my mind again, and again, and again," the man said of the abuse, in a powerful victim impact statement read in the ACT Supreme Court.

"Sleep is not something I look forward to ... but I can't share the reason why."

The man spoke as he sat metres from his abuser, Garry Leslie Marsh, 72, who was found guilty in August of 10 indecent assaults and one act of rape after he repeatedly molested the student, then 13, at his home and in a classroom in the 1980s.

Marsh, whose bail was revoked after the sentence hearing on Monday, has maintained his innocence.

He said in the witness box he "never, never" abused a child and his response to the victim's statement was "disbelief".

But his victim told him: "I will never forgive you ... The taking of my innocence for your own personal pleasure cannot be forgiven".

"I will never forget you or the evil things that you did, and the impact your selfish actions have had over me for my entire life.

"I can only hope that now you will live with the effects of your actions all those years ago for the rest of your life, as do I."

He said while the events of those years didn't define him, the memories crept into his dreams every night and had "invaded every part of my being".

The man had turned to drugs at school as an escape "during the periods when I wouldn't turn off the images in my mind". Later, he self-medicated with alcohol and still had up to eight beers and "a few spirit drinks" every night to help him sleep.

He had been diagnosed with post-traumatic shock disorder, which he said could explain his erratic sleep patterns, dramatic mood swings, severe anger outbursts and "extreme" reactions to everyday events.

He said his family continued to bear the brunt of those day-to-day behaviours and was sure they had damaged his relationships with his partner and children, with whom he could "never share the true reason Dad does what he does".

"Because of the shame and self-blame that I still experience, sometimes it is easier for me to just find a place to be alone and just cry.

"Without my family I doubt I would be here today, as I suspect the demons and memories I carry would have won and I would have taken an easier path that many others do and I would not be here at all."

Marsh told the court he suffered health problems and was sole carer for his mother, aged 95, who refused to go into an aged care facility and was "totally dependent" on him.

Prosecutor Jane Campbell said Marsh's offending was a "gross violation" of his "position of trust and authority".

She said Marsh had groomed the boy, talking about his sexual development and inviting him to his home and abusing him "for his own sexual gratification".

Ms Campbell said the man's statement "speaks volumes as to the long-term impact of child sexual abuse".

"He has suffered his whole entire life from the time this occurred. What happens to a child when they are sexually abused - that child is lost."

His defence lawyer, Greg Walsh, acknowledged the offences were "extremely serious" and involved a "gross breach of trust".

He said the boy should have been treated appropriately, with dignity, and "not in the manner that he was".

Mr Walsh said he couldn't argue against full-time custody, but asked the court to "offer some mercy" given Marsh's age and his mother's condition would make prison "a very difficult process, a very difficult time in his life".

Marsh was remanded in custody. Justice John Burns will sentence him on Friday.

An edited excerpt of the man's victim impact statement

"Where to start?

Let me start by saying that your actions of all those years ago have had a lifelong effect on my life, and of those around me.

I am not a forgiving person and I want to make it clear I will never forgive you; my childhood is something I can never have back and will never get to re-do. Your actions and thoughts robbed me of one of the basic rights of all children, to be a child, and the taking of my innocence for your own personal pleasure cannot be forgiven.

The events of those years ago creep into my dreams every night, and have invaded every part of my being. While they do not define who I have become as a person, they are an unwanted part of me that I can never escape or remove, and will never leave me.

I cannot show the physical scars from the events of all those years ago, but to me they are just as real, they will never heal, and unlike the physical ones there [is] more to these scars than what you see on the surface.

After you were dismissed from the school I was left to carry on as though nothing happened, you were the lucky one. The embarrassment, the shame and self-blame that I experienced then, and through to this day, was never-ending and the horrible reminders of what happened have never left me. They stayed with me every time I walked through the corridors, went to the gym or sat at the bus stop after footy training for all of my time left at the school. During this time I was reminded of what you did and had to live with the fear that others would find out.

Prior to your actions I used to enjoy school, it was fun and something I used to look forward to. And while there may have been periods of relief, and to many it appeared that I was happy and relaxed, school ended up as something I just needed to get through, and survive, rather than experiences to remember and look back on with any fond memories.

To this day I still cannot bear to be within the walls of St Edmund's as the memories of what occurred keep flooding back.

I will never get to change the past and this journey is not about that, and certainly over the last few years, since starting this legal course of action, my life and mental health have dramatically changed as well as impacted the lives of those around me and not for the better.

It is a painful process and I am not sure I would recommend it to anyone else.

I cannot put into words the negative emotions and feelings that I battle with daily, and will continue to experience for many years to come. I will never forget you or the evil things that you did, and the impact your selfish actions have had over me for my entire life. As I stated at the beginning I am not a forgiving person, I can only hope that now you will live with the effects of your actions all those years ago for the rest of your life, as do I."

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