Peter Gray, who is also acting for the Catholic Church's Truth, Justice and Healing Council, cited a medical report that had not been previously lodged with the commission to suggest former Marist College Canberra student, Damian De Marco, had once been a heavy marijuana user and this may have affected his memory of conversations with senior Marist Brothers in 1986 and 1993.

Mr De Marco, aged 45, was a student at the college in the 1970s and '80s. He told the commission Brother Kostka Chute had taken him into a store room at the college, hugged him and then tried to put his (Kostka's) hand inside his trousers in 1981.

Mr De Marco had not disclosed this until 1986 when he was in year 12 and was concerned Chute might have been molesting another student.

Mr De Marco told the hearing he had gone to his year master, John Doyle, and told him of his own earlier experience and his concerns for the welfare of the year 7 boy he feared was being abused.

He said he told Mr Doyle, "I'm really worried about this year 7 boy; I have been watching him for quite a while and have a strong suspicion that Brother Kostka might be sexually assaulting him. Can you find out if he is ok?"

Mr Doyle subsequently told Mr De Marco he had passed the information on to headmaster Brother Terrence Heinrich, who had spoken to Brother Kostka. Brother Kostka had denied the allegations and Mr De Marco said he was told nothing would be done. "I was dumbfounded," he said.

In 1993, on hearing Brother Kostka was still teaching, Mr De Marco said he had tried again. This led to a meeting with Brother Alexis Turton, the provincial, or head of the Marist Brothers from 1989 to 1995, at the Qantas Lounge at Canberra Airport.

Mr De Marco said Brother Turton told him Brother Kostka had denied the allegations (of the 1981 incident), that no other alleged victims had been found and that he (Kostka) was now at the Marist headquarters in Sydney where he would have no further contact with children.

In 2001, on learning Brother Kostka was apparently running "some kind of drop-in centre" at a Marist facility near Mittagong, Mr De Marco went to the police and made a complaint. He said the police later told him they had not been able to locate Brother Kostka.

Mr Gray put it to Mr De Marco that he had told a psychologist he (De Marco) had been a heavy marijuana user and, on occasion, had consumed up to "50 or 60 cones a day".

Mr De Marco said he had been only a recreational user of the drug and it had not impaired his memory of what happened in 1981, his conversation with Mr Doyle in 1986 or his conversation with Brother Turton in 1993, in any way.

"I can picture to this day what happened in that store room," Mr De Marco said. "I could draw a diagram. I have an extremely vivid memory of my conversation with John Doyle; I have an extremely vivid memory of my conversation with Brother Alexis Turton."