The detail appears to have been missed by judicial and police staff, who arranged for Livingstone to do a 12-week domestic violence course to earn a waiver.
The granting of diversion is one of the issues being probed in an investigation into the deaths of Bradley, 9, and Ellen, 6, who were killed by their father in their St Leonards home before he took his own life.
The killings came last month when Livingstone stormed into the family home, from which he was barred by a protection order taken by wife Katharine Webb.
The detail emerged during a New Zealand Herald search of the court file relating to Livingstone's two breaches of the protection order taken against him.
The first was dealt with through the police diversion scheme, meaning he escaped without conviction. The second time Livingstone breached the order, he was given a discharge without conviction.
The apparent error over diversion for the first breach may have led to Livingstone receiving lighter treatment for the next breach.
He was twice able to flout a court order and approach Ms Webb without gaining a conviction.
Police prosecutor Katherine Saxton had opposed the discharge without conviction, telling the court a mistake had been made over his earlier breach. "The police diversion scheme prohibits diversion for breaches of court orders therefore this matter should not have been resolved this way."
Livingstone's lawyer had argued a conviction would cost him his job at the Department of Corrections.
But Ms Saxton said Ms Webb objected to her estranged husband being let off without a conviction. "She states it took a lot of courage to call the police on each occasion."
A police spokeswoman confirmed that diversion should not have been available.
"This is because a breach of a court order is viewed as a serious incident and indicates that an offence against someone has occurred - hence there is no policy, practice or ability to consider diversion in these circumstances."
Detective Inspector Steve McGregor said the issue was part of the police's investigation.
Police interview full of contrition
"I am sorry I upset Kath."
The plaintive words are captured in a police interview of Edward Livingstone after he breached for a second time a protection order taken out by his estranged wife Katharine Webb.
The interview, on September 14, records his admission he breached the order. "I broke down," he told Constable Mark Tuten. "I couldn't rationalise anything."
He also minimised a prior breach of the order, saying he had simply emailed Ms Webb. In reality, he staked out the neighbourhood from which he was banned and went on to the family property.
In the second breach, he admitted ringing her. "I said I loved Bradley and Ellen. What happened between us, wasn't me that done it. It was a reaction to the Zyban [stop-smoking medication] that made me psychotic."
The reference, repeated in a November court affidavit, appears to relate to a May incident for which he was detained for psychiatric treatment. A doctor's letter on the file refers to Livingstone stopping the medication.
"This offending was largely caused by my untreated depression and inability to rationally deal with my relationship break-up."
- David Fisher of the NZ Herald