At the opening of the case, the prosecution said a feature of the case was the manner in which O'Brien had engaged with the young men and how he groomed them and developed inappropriate relationships and favoured certain students. This involved giving them alcohol and taking them to the pub.

Prosecuting counsel Anne-Marie Lawlor said it ultimately involved the young men staying with him and waking up to find themselves being molested and sexually assaulted.

Three of the complainants were students aged between 17 and 18. Another was a 19-year-old who had left school. Two other complainants, an 18-year-old and a 24-year-old were not students, but knew O’Brien from his home town.

Ms Lawlor told the court that the ages of the complainants in the case meant they were old enough to consent, but the prosecution said in these cases there was no consent and that consent cannot be given when a person is asleep.

In closing arguments, Ms Lawlor told the jury they must put aside any sympathy they may feel and look at the evidence dispassionately.

She told the jury they must consider if O’Brien sexually assaulted the six complainants and attempted to rape one of them.

Ms Lawlor asked the jury to consider whether "there is an inherent unlikelihood that several people would make similar allegations" against the same person.

She said there was "an implausibility of a number of people making up the same allegation against one person".

Ms Lawlor said it was significant that the accused "made a very considered and deliberate decision to lie repeatedly to gardaí" for "no reason but to protect himself".

She said the complainants had each given "compelling" and credible evidence about the alleged incidents. She asked the jury to consider if any of them can come to tell them a "pack of lies".

"Why don't you just sleep on the bed"

In his closing argument, defence counsel Michael O’Higgins told the jury his client’s decision to lie to gardaí was partly because he was terrified by the ramifications.

Mr O’Higgins said his client had acknowledged his contact with some students was "completely inappropriate" and suggested "not everyone is the same level of emotional maturity".

He suggested that a person's level of emotional maturity and their physical age may not match and that his client was "not very mature".

He also asked them to consider if there are inconsistencies in the evidence given by the six complainants of the alleged incidents. Mr O'Higgins suggested to the jury that they must also consider the background circumstances, including the difficulties that gay people faced in Ireland during the 1990s.

The jury heard evidence from six complainants including a then 18-year-old man, who said he had stayed at his teacher's home in November 1997.

The young man assumed that he would be sleeping on a couch, but he was told when he reached the home that he could sleep on the bedroom floor of his teacher, who then said "why don’t you just sleep on the bed?"

The young man thought this was an "unusual situation, as he was my teacher and I was his student", but "I just went along with it".

He went on to describe how he awoke to "rustling in his boxer shorts" and he "froze to the spot".

The man said when it happened a second time he jumped out of bed and asked what the hell he was doing. The complainant described being in "total shock" and "incredibly upset".

He said he ran from O’Brien’s house and told his mother he had been "raped", but he understood that was not what had actually happened.

His mother made contact with the school and the principal visited the next day and told him to write down what had happened. He did so and gave it to the principal. He said the next time he saw that statement was when the gardaí made contact with him in 2019.

Asked why he had not made a statement to gardaí sooner, the man said he did not feel he was mature enough to come forward and did not want to relive the experience.

Principal gave evidence about complaint

The principal in the school at the time told the jury that he received a call to his office one afternoon telling him that there had been an incident the previous night that involved "sexual contact between a teacher and a student".

He visited the student’s home, but said he could not remember what was said. When shown a statement made written by the student at the time, he agreed those were the allegations made.

The complainant said he returned to the school and spoke to the school solicitor. He said the accused had called in sick that day and he called to his home to see him that afternoon.

The complainant told the jury that he cannot recall exactly what he said to the accused, but he said what O’Brien said to him stuck in his mind.

"He said to me – 'is it P45 time?’ I said 'I am afraid it is'. I can’t remember anything before or after that," the man continued. He confirmed that the accused never returned to work as a teacher in the school.

The witness agreed with defence counsel Mr O’Higgins that there was "a drinking culture in the school" at the time that would not be approved of today.

Complainant tells court of 'shock and shame'

The fourth complainant to give evidence said the accused was his teacher in Junior Certificate and later had contact with him through school musicals. The then 17-year-old said he socialised with O’Brien and they would skip class on Wednesday afternoons and go to the pub.

He said one night in 1995 they drank eight or nine pints and returned to his house where they slept in the same bed.

He said he woke the following morning to find the accused performing oral sex on him. He said he was in a state of shock and delirious. He was then told by the accused man: "It’s your turn now." The young man then performed oral sex on the teacher.

The man said he later left and could not process what had happened. There was an element of "shock and shame so I bottled it up and said nothing", he said.

He said he did not have any contact with the accused over the summer months and when he returned for his final year he left after a number of hours.

The man told the school principal he was leaving and was not coming back, but he said the principal tried to convince him not to leave and said if he left he would have to tell his mother about his cannabis use.

He said he went home to his mother and said: "I have a few things I have to tell you". He then described telling his mother "everything". The jury heard that the witness made a statement to the gardaí in April 2019.

The complainant was asked by counsel why he had not come forward before this. He said: "I was ashamed, and after a year and a half of therapy, I had convinced myself that there was nothing to be ashamed about and not to bottle it up any longer."

During cross-examination, the witness agreed that there were other sexual encounters at the accused man's apartment, but he could not recall specific details. The jury was told there were no crimes alleged in relation to these subsequent encounters.

"I would have trusted him with my life"

The sixth complainant in the case told the jury that he developed a close friendship with his teacher when he was in transition year.

"I completely and utterly trusted him. I would have trusted him with my life. I had nothing to fear; he was a great schoolteacher, and I had no issue spending the night in his house," he said.

He told the jury that he had been to the accused’s house on two previous occasions, but on this particular occasion, he was due to stay the night as it was late. The witness said he was in fifth year at the time.

He believed he would be sleeping in the spare room but the accused told him there was no need and to "jump in here".

The witness said he got into the opposite side of the bed and he was uncomfortable with this and planned to go to the spare room once the accused was asleep.

He said he fell asleep, but later woke to find the accused "with his head down on my crotch giving me a b***job".

He said he was "scared s***less and frozen solid in the bed". He continued: "In my head, I kept saying stop, stop, stop". When asked by counsel if he had consented to this, he said, "absolutely not".

The witness said he was unsure how long this went on for and turned around to lie on his stomach. He said he believed that by lying on his stomach, this would stop what was happening.

He then told the court that the accused "climbed up on top of my back". He described feeling the accused’s head on his shoulders and his stubble and said the accused was trying to manoeuvre himself into a position to "do something".

When asked by counsel if the accused did manage to manoeuvre himself, he replied "yes" and told the jury that the accused manoeuvred his penis towards his backside.

The witness said his "face was in the pillow", "my heart was racing, and I was frozen".

Further complaints against accused

Another 18-year-old who knew the accused from his home town said in 1991 he was staying over in his house and woke in similar circumstances.

A then 24-year-old said he knew the accused from a group and he woke up to his face being licked followed by what the prosecution said was a sexual assault.

A then 19-year-old who had left school at the time said he was molested in a toilet cubicle in a pub.

In the witness box, O'Brien said he had initially lied to gardaí, denying any sexual encounter with any of the complainants, because he had panicked.

He said he had gone into a "sort of blind panic about it all".

O'Brien told defence Mr O’Higgins that he had initially denied any sexual contact because of shame, but later provided statements of clarification admitting sexual contact with three of the six, which he said was consensual.

He said the other complainants were either mistaken or lying.

O'Brien also denied telling a female friend that he had made a pass at one of the complainants and said it was his view that she had fabricated this.