On the eve of the findings being made public, the Defence Department is seeking to block publication of key evidence relating to the "insider" killings in central Afghanistan on August 29, 2012.

Private Robert Poate, Lance Corporal Stjepan "Rick" Milosevic, and Sapper James Martin died when they were gunned down without warning by one of the Afghan soldiers they were supposed to mentor at Patrol Base Wahab in Oruzgan province.

The deaths have been the subject of a first coroner's inquest into Afghan combat casualties.

And next week Queensland Deputy Coroner John Lock is due to release his findings from the inquest, which involved 10 days of evidence and received numerous submissions.

But earlier this month, lawyers for the Commonwealth government sent a lengthy letter to Mr Lock arguing that significant parts of the inquest's brief of evidence be kept confidential on the grounds of national security.

The request goes directly against the wishes of the soldiers' next of kin who have called for Mr Lock, after he releases his findings, to make public the brief of evidence that includes key documents like witness statements and investigation reports.

​Mr Lock's office on Wednesday (September 16) confirmed receipt of requests from various parties.

But a spokesman for the Queensland Coroner's Office said Mr Lock had not made any decision about those matters.

The inquest, which was sought by the families of the deceased soldiers, represents the first time a public civilian-led inquiry has delved into little known military procedure and operations in Afghanistan.

During the inquest, however, soldiers' next of kin and their lawyers have been intensely frustrated with having to navigate a minefield of secrecy laws and suppressions while trying to uncover the truth.

Numerous examples can be found throughout the inquest where the Commonwealth has successfully asked to close the court or impose suppression orders in relation to key evidence and witnesses that has made uncovering the truth difficult.

One glaring example relates to the contents of special orders that the ADF has been successful in having suppressed and some emails between high-level officers about the orders.

The order, known as "Fragmentary Order 13", was issued by the International Security Assistance Force (ISAF) and was aimed at ensuring soldiers took a extra precautions against insider attacks – some of which may have prevented the deaths at Patrol Base Wahab.

The order was also considered critical as it was issued in the weeks before the attacks.

But exactly how top-level commanders reacted to this order was difficult to discover because of secrecy.

One potential line of inquiry related to the actions of the senior officer required to react to and circulate the intent of the orders.

This officer, who can only be called X as his name has been suppressed, made significant efforts to circulate the concerns raised by the orders, some two weeks before the fatal attacks.

Counsel assisting even went so far as to allege that X had a disagreement with the then task group commander, Colonel Trent Scott, about the circulation of a draft order.

X was alleged to have written an email alleging that Col Scott had crossed out parts of X's draft order and described parts of it as a "no shit statement", according to a submission to the coroner by counsel assisting.

Counsel assisting also suggested that this, X's email, was a "cover your arse" type of statement.

However, this could not be confirmed as X was not available to give evidence because of health reasons.

The emails have been classified as "protected" and have never been released publicly. Fairfax Media understands they are not to be found even in the brief of evidence.

A direct quotation from the email is also protected and cannot be published.

Lawyers for the Commonwealth in their submission have vigorously rejected the email allegations, arguing that X had written the email because he was directed to review the task group's progress.

"Selective quotation of that email, out of context, places emphasis on possible criticism of Col Scott purportedly intended by its drafter," they say.

They have also rejected the "cover your arse" claim, saying that was "simply a theory" put forward by counsel assisting and that the officer who wrote it could not be questioned.

"[X] was unwell and was excused from the inquest – his absence should lead to increased caution in making findings, comments or recommendations."

The Commonwealth lawyers also argued that counsel assisting did not put the "supposed subtext" of the email to Col Scott.

The Commonwealth's push for secrecy appeared to frustrate the coroner at times.

In one instance, counsel for the Commonwealth James Renwick, SC, demanded that any discussion about the dimensions of Patrol Base Wahab be conducted in closed court.

When this was queried by Peter Bodor, QC, for the Poate family, Mr Lock stated: "It's just difficult to know what is and isn't [redacted] at times."

To which Mr Bodor replied: "It [the secrecy] is difficult to understand two years after the event about a base that's been abandoned anyway."

The demands for censorship are understood to have deeply distressed the dead men's families who have been allowed to view certain secret files but have had to give an undertaking not to disclose the information.

They were further distressed when during inquest hearings last year Brigadier Mark Holmes summonsed the families into a private room and threatened to "reference" the family to the Commonwealth Attorney-General unless they removed a reference to a secret mobile phone issue in a submission put forward by the Poates.

Mr Lock later described the action as "inappropriate".

Defence on Friday declined to respond to questions about the emails and the move to try and censor the brief of evidence with a spokesman saying: "It would be inappropriate for Defence to respond to these questions as these are matters to be determined by the Queensland Deputy Coroner."

Counsel assisting's final submissions have alleged eight failings by Defence including inadequate training and mission planning and not enough known about the patrol base failure to ensure separation between Afghans and Australians, too few Australian troops and a failure to understand the guardian angel concept.

The Commonwealth for Defence rejects the allegations arguing the threat of insider attack had been recognised and force protection measures were adequate. It also rejected claims that wearing of body armour would not necessarily have saved the victims and that recommendations will prevent deaths in similar circumstances.