The alleged victim did not go into detail with the school headmaster at the time and then kept his silence after Garry Leslie Marsh's termination.

The ACT Supreme Court has heard that coverage of the Royal Commission into Institutional Responses to Child Sexual Abuse stirred memories and prompted the alleged victim to report the matter to police 35 years on.

But the defence says this passage of time disadvantaged the accused as it made it harder to challenge the allegations.

Marsh, 72, of Sydney, is on trial before Justice John Burns accused of indecent assault and buggery.

He has pleaded not guilty.

One count of indecent assault was dropped during the trial earlier this week due to lack of evidence.

The abuse allegedly took place between 1979 and 1980 when the alleged victim was aged about 13.

Jurors have heard Marsh – who had been the boy's school teacher and football coach – had struck up a friendship with the teen after his parents separated.

The boys mother worked long hours and he would spend time at Marsh's home, receive lifts to football, and on one occasion, slept over.

The Crown alleges that Marsh used this relationship to indecently assault the boy on six separate occasions.

The court also heard allegations that Marsh would watch the boys in his care shower and change after physical education and would grab at their groins and buttocks as a game.

Prosecutor Jane Campbell argued this behaviour showed Marsh had a sexual attraction towards the alleged victim.

In her closing, Ms Campbell said the alleged victim had reported the allegations to his mother and a friend at the time.

The school had been notified and Marsh's position terminated.

He later left the country to work in Nauru.

Ms Campbell also pointed to a number of apparent contradictions between Marsh's statement to police and his evidence from the witness stand, including that no children had visited his home, the alleged victim had not slept over at his house, and he had not driven students in his car.

But defence barrister, Ray Livingstone, argued the prosecution's case had amounted to an array of allegations and had not discharged the burden of proof beyond reasonable doubt.

He said it would be appropriate for jurors to return verdicts of not guilty.

Justice John Burns gave jurors final directions and sent them to deliberate on the fate of Marsh on Thursday afternoon.

The jury were sent home for the night about 4.30pm and will reconvene to continue their deliberations on Friday morning.