He sought special permission from the court to take the prosecution outside the usual legal time limit after the then-Department of Labour misunderstood it was responsible for investigating the crash and did nothing.
It emerged Flight Lieutenant Madsen had only a half-a-second warning of danger that he was 50 feet from the ground but would have had 19 seconds to react if he had followed Defence Force Orders and set the alarm at 200 feet.
Prosecutor Tim Mackenzie told the court the air force's failure to eliminate the "can do" culture at 3 Squadron "which may have led to personnel believing it was appropriate to breach orders and flight plans to complete tasks".
Ben Carson
The court was told the air force had no system which would allow those in charge of authorising flights to judge whether or not personnel were qualified for the duties they were being asked to perform.
It was also alleged the air force had failed to follow its own processes which would have seen the flight path checked the day before to familiarise crews with the path they would travel.
Mr Mackenzie also said there was no appropriate risk management system for indentifying risks when flying with night vision gear.
Video: Anzac Day Iriquois helicopter crash
In the wake of the verdict, the parents of Ben Carson, Andrew and Pauline, praised Mr Creeggan for taking the case.
"Without Stevin, it would have been swept under the carpet."
Mr Carson said the four men on the flight deserved "respect" from their employer - the air force - and called for an overhaul of the military justice system, which has seen no one convicted for the failures which led to the deaths.
NZDF accepts responsibility
The Defence Force said in a statement this afternoon that it accepted responsibility and unreservedly apologies for failing to prevent the crash.
"As an organisation we did not do all that we could to ensure a safe working environment for our people," said Chief of Air Force Air Vice-Marshal Mike Yardley.
"We have pleaded guilty to failing to prevent this accident and we have unreservedly apologised for our shortcomings. I reiterate that apology to all of the next of kin and to Sergeant Creeggan," he said.
"The effect of this tragedy on the families of those lost, and on Sergeant Creeggan, will never go away. The only amends Defence can make is to ensure that the lessons of this tragedy also never go away. We have committed wholeheartedly to do that: part of the legacy of this accident has been a complete overhaul of the Defence Force's approach to safety.
"We owe that to the crew of Iroquois Black 2, we owe it to the families, and we owe it to our Defence Force," he said.
He said the failure could not be laid at the door of any one person or small group, but was organisational. "A variety of related flaws in our systems failed to prevent a fatal event."
Air Vice Marshall Yardley said the Chief of Defence Force had established a Defence-wide Directorate of Health and Safety.
"In the Air Force, our Flying Orders have been completely re-written. Improved risk-management assessments for all flights have been introduced, and a new operating airworthiness unit has been put in place to supervise the management and safety of all air operations at Ohakea, in line with similar units at our other bases.
"We have to be an organisation that is looking far ahead for risks to our people, long before they become an accident. We owe it to the crew of Iroquois Black 2, we owe it to the families, and we owe it to our Defence Force and the New Zealand people."
