The state's highest court has ruled a five-year-old boy was perfectly capable of telling the truth when revealing how his mother's de-facto husband had sexually abused him.
The offender claimed he should not have been convicted by a County Court jury in May last year of six counts of incest because the boy was too young to understand the concept of truth.
The man, who was jailed for five years with a non-parole period of three years and four months, appealed against his conviction and sentence, suggesting the boy may have also been coerced into making the allegations against him during two VAREs (visual and audio recorded evidence) conducted with a trained police officer.
The Court of Appeal's president Justice Chris Maxwell and Justices Marcia Neave and Robert Redlich, in a judgment handed down on Tuesday, dismissed the man's appeal.
Justice Redlich said the man, 27, had been in a de facto relationship with the boy's mother and they had lived together.
The boy was aged four when the abuse began in August 2009 before he told his uncle what had been happening in June 2011.
When the boy first revealed the abuse, he was told if he was lying he would get into trouble and was asked the next day to repeat his claims in front of his family.
According to his uncle, the boy "nearly started crying, his eyes welled up and he said 'I don't want to"'.
After being encouraged by his uncle and his father, the boy repeated the abuse claims.
His family asked him questions about the alleged incidents for about 10 minutes before his aunt took him into another room and questioned him alone.
She said that if he was lying, no one in the family would talk to him. He started crying and said that the allegations were true.
Justice Redlich said that during the VAREs, a number of scenarios were put to the boy to see if he understood what telling the truth meant.
The judge said that in one of the scenarios, the boy understood that it would be a lie to say he arrived at the police station in a helicopter.
"He said that 'The truth is that I came in a car'," Justice Redlich said.
"The trial judge ruled that the complainant (the boy) had the capacity to give truthful evidence and was a competent person to give sworn evidence. His Honour was plainly correct."
Justice Redlich said that during the VAREs, the boy, as was to be expected of a five-year-old, was prone to often give answers that were quite unclear.
"He was often distracted and failed to respond directly to the questions.
"Many of the purportedly 'leading' questions were attempts by the interviewer to refocus the complainant's attention.
"In each of the examples cited by the applicant, the interviewer asked the complainant to elaborate on an allegation he had already made voluntarily."
The judge said there was nothing in the VAREs "to suggest that the evidence adduced from the complainant was obtained in an improper manner, such that its exclusion might have needed to be considered".
"The complainant was encouraged to begin by way of a free narrative, and then was asked direct questions in order to isolate specific incidents or issues.
"Any information raised by the interviewer in her question had already been asserted by the child.
"The police interviewer maintained an appropriate line of questioning without being unnecessarily or improperly suggestive.
"The interviewer was entitled to ask open questions that were intended to exhaust the complainant's memory.
"There is no substance in the contention that any of the allegations made by the complainant were the result of improper leading and suggestive questions."