A coroner's inquest has heard Edward Livingstone told friends he intended to kill his children but kept that from his psychiatrist.
Edward Livingstone, 51, was found dead with his nine-year-old son Bradley and six-year-old daughter Ellen at their home in the suburb of St Leonards in January last year.
On the first day of a four-day inquest held in Dunedin, coroner Deborah Marshall said she wanted to know why crucial pieces of information were either withheld or deliberately ignored in the lead up to the deaths.
The inquest heard Livingstone had told friends he intended to kill his children, but never said this in extensive sessions with psychiatrist Christopher Wisely.
Under cross-examination, Dr Wisely admitted he had probably been deceived by Livingstone.
"I don't know if he deceived me completely but I suspect on some areas he certainly was deceptive."
The inquest also heard Livingstone twice appeared before the court for breaching a protection order.
On the second time he appeared in court, he was discharged without conviction and the judge at the time was unaware he had previous convictions for violence and arson while living in Australia.
Sergeant Kate Saxton told the coroner she had not asked for an adjournment to check Livingstone's background for convictions.