Work and Income staff shot dead by Russell Tully would have had time to escape if the Ashburton office had "controlled" access, a WorkSafe lawyer has said.
However, Ministry of Social Development lawyer Brent Stanaway told the Wellington District Court it had not been established any sort of delay would have enabled that.
Peggy Noble and Leigh Cleveland were killed in the office on 1 September 2014.
Tully, who was found guilty of their murders, was sentenced to life imprisonment and ordered to spent at least 27 years in prison before being eligible for parole.
The ministry pleaded guilty at a hearing last month to a charge of failing to take all practicable steps to ensure its staff were safe, but it disputed WorkSafe's claim the Ashburton office's layout was unsafe for staff.
Today, both sides made closing submissions before Chief District Court Judge Jan-Marie Doogue.
WorkSafe lawyer Dale La Hood said Chief Judge Doogue would have to determine what sort of hazard to staff the Ministry of Social Development should have contemplated as part of its workplace safety preparation.
He said the ministry's suggestion that the threat response should remain at the level of people without weapons was unsustainable.
Mr La Hood said WorkSafe's experts had shown that a controlled access could work in conjunction with the office's open-plan nature.
"In analysing the threat level, the experts said that which had to be controlled for was person with a weapon at the very least."
However Mr Stanaway said Tully had a weapon capable of breaking down solid walls.
"Even if a guard had been in place ... he would have been shot ... the front door would have shattered in a second and Tully would have got into the office."
Mr Stanaway said the very short timeframe of the incident left no basis on which the court could conclude beyond reasonable doubt that those shot and injured would have been able to run and escape rather than hide.
He said the Ashburton office had a small number of experienced staff who knew their community well and could not have predicted Tully's actions.
The judge has reserved her decision.