A key witness in the investigation, says the external investigator's limited powers, as in all council code of conduct inquiries, falls well short of being able to produce conclusive results.

Newcastle Maritime Museum Society president Bob Cook was the first person to give evidence in the independent investigation carried out by workplace relations firm Pinnacle Integrity.

It's unknown how many other people took part in the investigation, the only other participants known to the Herald are council boss Jeremy Bath and letter writer Mr Neylon.

Mr Cook broke his silence on the confidential investigation this week after he learned the process had been finalised and council had the investigation report.

While saying he had "complete faith" in the experienced former police officer carrying out the investigation, Mr Cook said he had no faith in the process due to it's "severe limitations".

"It was doomed to fail from the beginning, because it wasn't a compulsory interview process," he said.

"That's fundamentally the problem I saw straight away. That it could not compel people to participate, to answer questions or produce evidence.

"I was told at the time that I didn't have to answer any questions I didn't want to."

In accordance with the council's code of conduct policy, all of the investigation and its deliberations were held in secret.

The terms of reference, which also remain a secret, were set by a combination of information provided by the council and a letter from the Minister for Local Government Ron Hoenig.

The investigation was launched into Mr Bath's connections with misleading letter writer Scott Neylon, who has lived in Japan for decades, after a motion by Labor councillor Carol Duncan at the July Newcastle council meeting.

Mr Bath has been best friends with Mr Neylon for 25 years. The Herald revealed in July that dozens of letters and online comments have been published in media outlets over 13 years under the name Scott Neylon, which twist the truth, distort reality and follow Mr Bath's career progression, attacking his critics and supporting his employers.

According to a motion from council's Tuesday night meeting, the investigation found "no evidence that the CEO incentivised the author to write the articles".

"Having considered the available evidence, the investigation found insufficient evidence to support the allegations," the investigation outcome reads.

The Newcastle Herald was not contacted as part of the investigation, meaning the investigator did not access the 19 letters - which are at the heart of the scandal - sent to the Herald over nine years, many of which remain unpublished.

Pinnacle Integrity did not respond to questions about why it did not seek access to the letters.

"Pinnacle Integrity, as conduct reviewer, can confirm that the evidence relating to the matters under inquiry were sufficiently and thoroughly investigated in accordance with the procedures," a spokeswoman said.

"The investigation process and evidence relating to the matter remain confidential."

According to Mr Cook, another key area of concern was how witnesses gave evidence.

Mr Cook was interviewed in an online video call, but it's unsure how other witnesses took part in the investigation..

"I was told that at any stage I could just make a written submission," he said.

"So there was nothing even compelling a face-to-face interview or anything like that.

"The investigator is hamstrung in a lot of ways and working in a government system that has a lot of constraints in an effort to get to the truth. Of course this raises questions about how reliable the outcome of the investigation is."

Despite initially agreeing to a phone interview with the Herald, Mr Neylon later reneged.

He has only ever communicated with the Herald via email and regularly sidesteps questions he doesn't want to answer.

The long-term expat has offered no explanation for why he repeatedly lied about where he lived, or why his letters twist the truth and distort reality in an effort to strengthen his arguments.

It's unknown if Mr Neylon has ever lived in Newcastle, and why he has such a strong interest in the city since his work records indicate he has been teaching English in Japan since 1998.

Mr Neylon has never been a Newcastle Herald subscriber. Despite this, he claims to keep abreast with Newcastle issues by reading the Herald.

According to the writer, over the past ten years he's moved eight times throughout Newcastle. He's lived at three different addresses in the same suburb in Lake Macquarie, then Mayfield, Mayfield West, back to Mayfield, Waratah and for the past year claims to have been living in Stockton.

Within his letters are a host of inconsistencies, some of them plainly wrong, including declaring in February 2017 that he lived next door to Mr Bath, then just weeks later claiming he lived on the other side of Mr Bath's house.

It's a long way from Japan, where Mr Neylon's Facebook posts consistently depict him living with his wife since he began publicly posting in 2011. He does not appear to have children.

Mr Cook questioned if the investigator had any further powers than the Herald in terms of questioning and gathering evidence.

"It appears that Mr Neylon did cooperate in some way," he said.

"But just how much and what he was willing to produce is unknown. Only by seeing the report will we know and be able to have any confidence that they actually did get anything out of him at all."

In 2016, the NSW Ombudsman conducted a review into the NSW government's use of external investigators and found the process wanting.

The Ombudsman said the use of external investigators was increasing as many government agencies no longer had the resources or expertise to carry out their own investigations.

"From our experience and discussions with staff from a range of agencies it appears that contracting external investigators can be costly and may not always produce effective results," the report reads.

The discussion paper identifies a host of issues including: no clearly defined terms of reference, investigators failing to adhere to the terms of reference, investigators misunderstanding relevant legislative requirements, investigators failing to provide procedural fairness to individuals who are the subject of adverse findings and investigations appearing to be focussed on preconceived outcomes.

Other issues included: assumptions and findings in investigation reports that are unsupported by the available evidence, investigators failing to obtain relevant evidence that was readily available, including not interviewing relevant witnesses or obtaining relevant documents, and factual conclusions being drawn in investigation reports on the basis of evidence which does not meet an applicable standard of proof.

"Unfortunately where an agency finds it necessary to outsource an investigation, very little guidance material exists as to how this is best achieved, costs can be burdensome and we have seen that the quality of external investigations can be very poor," the report reads.

Another area of concern was council's engaging investigators to examine allegations about a councillor or staff member who the investigator had previously investigated.

"We have seen such practices result in accusations that there is a reasonable apprehension of bias in appointing that investigator," the report reads.

It's unknown how much the Neylon investigation cost City of Newcastle.

The Ombudsman's report said government agencies were responsible for ensuring investigations provided value for money.