Police have admitted significant failings in the handling of complaints about Edward Livingstone before he killed his children.
The admissions were made by the detective in charge of the shooting investigation, Detective Senior Sergeant Kallum Croudis at the second day of the inquest, in Dunedin, into the deaths of Livingstone, 51, 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.
Livingstone moved out of the Kiwi Street home in May 2013, and was under a protection order stopping him from contacting his former wife, Katharine Webb, when he killed his children.
Under cross examination (by Livingstone's ex wife Katharine Webb's lawyer, Anne Stevens), Mr Croudis accepted the police never recorded bullet casings handed to them by one of the children that Livingstone had given them at a supervised visit in July 2013.
He agreed it was a significant omission that could have led to Livingstone being prosecuted or stopped him being given a police diversion for breaching a protection order.
Mr Croudis also admitted that a rape allegation made by Ms Webb was not followed up by the CIB and probably should have been.
He said certainly some things could have been done better in that case.
Mr Croudis also confirmed Livingstone admitted to previous arson charges from Australia 30 years earlier when arrested for family protection order breach in August 2013.
Under cross examination he agreed that police not following up the arson charges for several months, nor alerting
the court of their existence, was a failure that might have been significant.
Earlier, the inquest heard Livingstone stole the shotgun he used to shoot his two children from a flatmate's gun cabinet.
Mr Croudis said the semi-automatic shotgun Livingstone used came from the home of Philip Mans, whom he had lived with until a week earlier and the for it key was hidden in a drawer.
He said Mr Mans was also the source of the gun canisters Livingstone gave to his children during a supervised visit in July 2013.
The inquest was told Mr Mans did not realise his gun had been stolen.
A police reconstruction of events on the day of the shooting shows Livingstone bought a red fuel container earlier in the day, then filled it with petrol.
The container was found unused by the back door of the Livingstone house in Kiwi Street.
Livingstone's doctor also told the inquest the drugs she prescribed were not likely to have caused him to have a psychotic incident.
Dr Lewis said she normally only saw Livingstone once a year but he consulted her three times in 2013, the year before he shot his children.
She said she prescribed him an anti-depressant, an anti-insomnia drug and a week later, a stop-smoking drug, Zyban.
She said Livingstone at one point rang her to ask for a letter stating that Zyban had been a cause of him raping his then-wife Katharine Webb, but she did not believe there was evidence of that.
Cross-examined about a list of known side-effects of Zyban in a psychiatry handbook that included psychotic effects, Dr Lewis said those were anecdotal case reports and she had not seen them before.
Doubt over reporting of death threat
Yesterday, neighbour Melanie Foot said Livingstone told her in about June 2013 of his plan to kill the children and former wife and that she called police immediately to report it.
Police had said they did not have any record of the complaint.
A woman, whose name is suppressed, told the coroner's court in Dunedin she had encouraged Ms Foot to tell police because she had heard the death threat plan directly.
She said Ms Foot told her that she had - but she still has a doubt that happened.
Earlier the woman said Livingstone had well-known mental health problems and was often obsessive and intimidating.
She said she rang the police and complained about the man's behaviour about six months before he shot his children because he seemed to feel he was entitled to do whatever he wanted.
The woman said the police told her to call the emergency 111 number if Livingstone did anything dangerous.
The inquest opened yesterday with evidence from Ms Webb, who said that during the 10-year marriage Livingstone had pressured her for sex, and she ended the relationship when he raped her.