The man, then 15, is accused of forcing the two cousins to put his penis in their mouths at a home in Belconnen sometime between January 2003 and September in 2004.

The accused, who cannot be named, pleaded not guilty to four charges and has denied the sexual acts ever occurred.

He has no criminal convictions, has never been in trouble with police, and has been described of good character.

In summing up the case, Supreme Court Justice John Burns said the allegations hinged on the evidence of one of the alleged victims.

The girl, then aged between seven and eight, is the only one to have given direct evidence on the alleged sexual offences.

She told the court through pre-recorded evidence that she had been playing hairdressers with her cousin when the defendant entered the room and told the cousins to play a game of putting his penis in their mouths.

She did not come forward until 2010, after high school sex education classes brought back memories for her cousin.

Justice Burns said the delays did not suggest the allegations were false, but did affect the ability of the accused to defend himself.

The time gap made it difficult to cross-examine the complainants, affected the memory of witnesses, and made it hard for the accused to say where he was or what he was doing at particular times.

The second girl, then aged five and seven, could not recall any knowledge of the allegations, but did talk of other sexual impropriety by the accused.

That evidence does not relate to the charges, and is being treated as context evidence, meaning it cannot be used to decide his guilt, or to judge his character.

The jury retired early Thursday afternoon.