A jury has retired to consider whether a priest who was caught by two children having sex with their mother decades ago committed an indecent act on a six-year-old boy.
The boy and his sister confronted their mother - who died more than 20 years ago - and Terence Thomas Keliher from the doorway of the bedroom in their house in about 1976, the jury heard at the start of the Brisbane District Court trial.
The version given by 84-year-old Keliher - or Father Terry as he was known to the boy - of what happened afterwards was "pretty incredulous in its entirety", crown prosecutor Elizabeth Kelso said in her closing statement on Tuesday.
"My submission is that you could just set his evidence to the side because frankly it's really absurd and ridiculous to think that that's how things transpired on that day," she told the jury.
The Crown's case is that Keliher was naked when he stood up, faced the children about a metre away and starting masturbating before ejaculating onto the boy's chest.
Ms Kelso said Keliher was able to say - in the context of "this accidental splashing" - exactly where his semen landed on the boy.
He had not grabbed any bedding or clothes to cover himself while knowing he was about to ejaculate.
"That perhaps is the most ridiculous story you have ever heard in your life."
Ms Kelso told the jurors they could accept the complainant's evidence as "truthful and reliable".
Keliher told the court he first met the boy when visiting the house to give the family financial assistance, but had been in a sexual relationship with the mother for a few years before the alleged offence occurred.
He usually visited the house when the children were at school and their father at work, he said.
He told the court he was "shocked and ashamed" at being interrupted by the children, but agreed the boy had walked in on the pair engaging in sexual acts previously.
On the day of the alleged offence - a school day when Keliher expected only the mother to be home - the two were interrupted in the bedroom by the girl screaming at her mother, he told the court.
Keliher denied masturbating and deliberately ejaculating on the boy, saying he held his erect penis so "the semen would not escape" while getting off the bed, but then turned to get his clothes.
"As I turned, I let go of my penis and that's when the semen splashed out," he told the court.
Keliher was "trying his best to avoid ejaculation", defence barrister Tony Glynn told the jury in his closing statement.
He said Keliher was "focused on getting dressed so that he could leave that embarrassing situation".
"Unfortunately in the process of getting dressed he used both hands to put on his trousers," Mr Glynn added.
"The simple fact is that he made the mistake of removing his hand and he ejaculated."
Mr Glynn said the jury could not put any weight on the evidence of the complainant who had first used the word "masturbate" to the prosecutor just weeks before the trial.
Instead Keliher's admission that the children had previously seen him engaging in sexual acts with their mother "goes to show his honesty as a witness".
Keliher is charged with one count of indecent treatment of a child under the age of 12.
The trial in its second day is being held before Judge William Everson.
