The High Court in Christchurch has heard that Laniet Bain told a teacher she had been raped and given birth as a result while living in Papua New Guinea.
The evidence was given by Paul Hewson, a former running acquaintance of David Bain, on Wednesday afternoon.
Mr Bain is on trial for the murder of Laniet and four other family members.
Mr Hewson was asked about conversations he had had with Laniet while at Bayfield High School.
He said Laniet also told him she had tried to kill herself and later that she was a prostitute.
But he said he did not entirely believe what she had told him.
The Crown is to call five witnesses on Wednesday. Most will give evidence regarding background about the Bain family.
One of those witnesses, the Bain family doctor, told the High Court he was not treating Robin Bain for depression.
Peter McLeod testified that he had not specifically seen Robin Bain, 58, about depression and was not aware of whether he had been seeing another doctor for treatment.
Dr McLeod confirmed that he knew some of the family had suffered from malaria while living in Papua New Guinea, and was subsequently asked by the jury if that illness could cause blackouts. He said he did not think so.
One of Mr Bain's uncles told the court why the decision was made to destroy the family home after the killings.
John Boyd said he was one of the executors of the Bain family estate and after the deaths he went to the prison to visit Mr Bain to talk about agreeing to get rid of the house.
Mr Boyd said Mr Bain agreed to the house being burned down, saying he felt no emotional tie to the property.
Wednesday morning was taken up with further legal argument.
Mr Bain is on trial for the murder of his parents Robin and Margaret, sisters Laniet and Arawa and brother Stephen, at the family home in Dunedin on 20 June 1994.
He denies the charges and says his father was the real killer, who then turned the .22 Winchester rifle on himself.
Mr Bain was convicted of the murders in 1995, but in 2007 the Privy Council quashed the convictions. A retrial was subsequently ordered.
The trial is in its 34th day.