The evidence was heard during the trial of indigenous artist Dennis Michael Nona, 41, who has pleaded not guilty in the ACT Supreme Court to two counts of having sex with a child and two counts of an act of indecency in the presence of children.

Crown prosecutor Margaret Jones told Chief Justice Helen Murrell and a jury that Nona had sex with the girl in her home in February 1996.

The Crown alleged Nona had sex with the girl in April the same year, causing her to get pregnant.

Ms Jones told the jury the child's pregnancy had not been discovered until September when she was examined by a doctor.

But in a recording from a formal police interview in March 1997, the complainant said she didn't know how she became pregnant and didn't remember having sex with anyone.

The girl told police she remembered waking up in her bed after a party the night before when men had been drinking, and being told she had had an epileptic fit, a condition she said she had been diagnosed with in 1995.

Before her pregnancy was discovered by a doctor, the girl was told she "looked a bit big" by her sister.

The girl told police she approached her teacher to ask how a woman became pregnant and what the symptoms were, and began to cry when she recognised she had had morning sickness and could feel something moving in her stomach.

The girl, who later had an abortion and said she was too scared to tell her mother about the pregnancy, told police she didn't believe Nona was at the party and described him as being "nice and friendly".

But in October 2008, the complainant decided to proceed with an earlier complaint against Nona after Queensland Police contacted her with DNA results.

Ms Jones told the jury in her opening submission the DNA results provided strong evidence Nona was the father of the child, despite the girl telling police she didn't know who the father was during the interview.

But Nona's barrister, John Purnell, told the court in his opening submission the young girl had "a crush on [Nona] and was keen" on the accused, despite admitting the circumstances were extraordinary, unusual and shocking.

He also said there was evidence the girl had told Nona she had had sex with him while he was drunk and could not remember.

Mr Purnell told the jury the case was weird, sad and shocking and said it was their task to determine "who is telling the truth and who is lying" about the incidents.

The defence told the jury the case was a matter of whether Nona intentionally, voluntarily, and knowingly had sex with the girl.

Nona is also accused of committing an act of indecency in front of two children aged 13 and 14 at the time.

According to the prosecution, the children were in the backyard of a property when Nona knocked on a bedroom window from inside to draw their attention, and then exposed his penis with his hand on it.

The trial continues in the ACT Supreme Court.