Obviously what happened is that Nugan made one last request of his murderer, to write a suicide note with a religious theme, which was granted by the murderer. The note does not make much literal sense because it was never meant to. In his last moments Nugan hastily wrote a coded message, that when deciphered will reveal all secrets concerning the case, including where the money is.

Doctoral thesis: http://eprints.qut.edu.au/15949/
contents: http://eprints.qut.edu.au/15949/1/01front.pdf
thesis: http://eprints.qut.edu.au/15949/2/02whole.pdf
more: http://drjiggens.com/in_a_time_of_murder.html http://drjiggens.com/the_banker_and_the_killer_kop.html http://drjiggens.com/the_mystery_of_nugan_hand_bank.html
as well as a book: The Sydney Connection: The CIA, drugs, Nugan Hand and the murder of Donald Mackay

There is a lot to go through here, so I shall make separate comments as I feel appropriate.

Firstly, as PrometheanStardust has pointed out, this is a work by a pro-marijuana activist, and if you have an even passing familiarity with the ideas they typically espouse ("marijuana opens your mind to great cosmic insights...man"), you're going to find it difficult to regard them as a very credible authority. In his doctoral thesis introduction he gives some indication of how steeped he is in the marijuana culture:

And to give some idea of the sorts of insights that can be attained from a publication like "The Australian Weed", courtesy of one JJ McRoach:

Notice that he is at pains to insist that the problem with marijuana isn't with marijuana itself, nor its users, nor certain ethnic groups, but capitalism and the media.

Ok, it didn't take us long to get into the realm of Strumian Omnilectics.

After two paragraphs stating the basic facts concerning Donald Mackay's murder, Dr Jiggens then leaps sideways into his hobby-horse issue of decriminalising marijuana for personal use, attempting to conflate the two issues under the belief that Mackay's death somehow scuttled the movement for all time. I suspect already that this is going to be the real theme of his articles rather than any serious investigation into the issues of organised crime and corruption that remain a public concern.

Somehow I don't think it's very necessary to review NSW parliamentary hansards or media commentary of the era to know that there were other issues of concern in the mind of the public to cause them to oppose decriminalising marijuana, as they do to this day.

The first article has little more concerning Mackay that we are not already quite familiar with from many other books, news articles, and TV investigative specials. Dr. Jiggens instead treats us to a special brand of baby-boomer mythology where marijuana was once an innocent in the Garden of Eden until corrupted by the Serpent of drug laws and organised crime.

Perhaps he should consider that he and his baby-boomer cohorts were a victim of their own success. They actively promoted marijuana use, and doggedly published articles in its favour, and so thanks to their efforts marijuana use increased, and spilled outside of their self-destructive little cult and spread amongst the broader underclass, ie. bogans. With widespread bogan usage it was therefore a lucrative market, and since it was (quite understandably) illegal, then of course organised crime is going to muscle in. If marijuana had been legal as he fantasises, then it would be cigarette companies muscling in and forcing the amateurs out via quality control regulations and taxes. The entire tone of his movement is the wilfully immature outlook of the idealist who obstinately refuses to engage with reality.

Jiggen's second article, titled "The Banker & The Killer Kop: The Murder of Don Mackay" is at pains to insist that Fred Krahe, a corrupt ex-cop, general underworld heavy, and part time source for the Fairfax paper, "The Sun" was the murderer of Donald Mackay. Nowhere in the six paragraphs that Jiggen's devotes to his assertion of Krahe being the killer does he mention that in 1986 it was James Frederick Bazley, a hitman who was associated with the Painters and Dockers Union in Melbourne that was actually found guilty and sentenced to life imprisonment for the murder of Mackay.

A brief biography of Bazley's career includes such activities as:

Bazely, born in 1924, was allegedly a hit man and also a target of pre-election union violence on the Melbourne waterfront in the early 70's.

He carries the scars of four bullet wounds suffered in Melbourne's bloody waterfront wars.

He stood with a gun in his hand and a foot on the ballot box the day of the Painters and Dockers Union elections.

Following the union ballot, Bazely, a supporter of faction leader Bill Longley was wounded in two separate ambushes.

In May 1972, he caught machinegun fire at the gate of his North Carlton home.

He had been beaten for the position of vigilance officer in that year's election.

Bazely pulled a bullet from his shoulder on the way to hospital.

He told police he did not have a clue who shot him.

A police officer said at the time: "He has been marked for execution by the underworld hiearchy. He was lucky this time. Next time he might not escape with minor wounds."

But that he did.

He survived another attempted hit, in September the same year, when struck by bullets as he sat in his car.

Bazely was jailed after anti-drugs campaigner Donald Bruce Mackay disappeared from Griffith, NSW. in July 1977.

He was also found guilty of the April 1979 murders of drug couriers Douglas and Isabel Wilson at Seymour, north-east of Melbourne.

The Wilsons' bodies were found in a shallow grave at Rye in 1979.

Bazely was sentenced to life imprisonment in April 1986 for the Wilsons' murder.

He received concurrent sentences of nine years for conspiracy to murder Donald Mackay, and four years for the theft of $260,000 from Downards Security in 1978.

Bazely's appeal to the Full Court in June 1986 against the murder convictions was dismissed speedily.

He had no chance of finding the $60,000 needed for an appeal to the High Court.

The crown alleged a conspiracy to murder  Mackay by Mafia identity and drug trafficker Giofranco Tizzone, with Roger Joseph, patron of the Victoria Police Gun Club, and Bazely as the hired executioner.

It was Robert Trimbole, head of an allegedly protected Italian marijuana syndicate in NSW, who ordered the hit. Police involvement in covering up that trade and murders related to it has since been proven.

In an interview between Tom Prior of the Sun, and Bazely in 1987, Bazely said, "I didn't kill Mackay and I didn't kill the Wilsons".

An interview can be found here where he asserts that he's innocent, and didn't murder anyone, blaming it all on Krahe.

It should also be pointed out that the TV series "Crime Investigation Australia", episode "The Disappearance of Donald Mackay" has dramatised Bazely's murder of Mackay, including the bungled first attempt where an employee of Mackay's furniture store was almost the accidental target, and was able to give a description of Bazely.

The only notable believer of Bazely's assertion is Jiggen's himself, where he claims to have discovered the true murderer, Krahe, as he asserts in a recently published book as reported in The Australian:

So basically Jiggen's two primary authorities concerning his claim that Krahe was the murderer of Donald Mackay are himself, and the man who was found guilty by a court trial.

So why should Jiggen's insist finger Krahe the crooked cop over Bazely the union heavy? It seems that Krahe just happens to fit Jiggen's conspiratorial worldview of a nexus of organised crime, prohibition, the police, media, developers, capitalism, all working in unison to give a bad rap to the freaky weed. Hence the style of histrionic prose and disconnected logic that Jiggen's employs to describe Krahe and his deeds, both real and alleged:

Photos of Fred Krahe are never a pretty sight. The Killer Kop had a big, ugly head and he was described by another NSW detective as ‘an evil bloke — a big, brooding bastard with an aura of power and evil about him’. Fred Krahe joined the New South Wales police force in 1940 and rose to the rank of Detective-Sergeant, establishing a reputation as a gangland enforcer feared in the Sydney underworld. David Hickie called Krahe the ‘king of crooked police during the Askin era’. Along with Ray Kelly, Krahe organised the abortion rackets, the armed hold-ups, the framing of criminals and the bribery payments among prostitutes and the police.

But in 1971 Krahe’s brothel madam, Shirley Briffman, blew the whistle on his rackets, subsequently paying with her life. Krahe retired ‘medically unfit’ from the police in 1972 and became a licensed private investigator, working as a security chief for the developers during the Victoria Street redevelopment/Green Ban battle in Kings Cross. In July 1975, Juanita Nielsen, whose local newspaper NOW had led the fight against the multi-million dollar redevelopment, disappeared. Many attribute the murder of Juanita Nielsen to Krahe, a murder with many similarities to the murder of Donald Mackay.

I myself voiced concern over Krahe being the accused, surprised you didn't quote that, but the new evidnece Jiggens introduces regarding Krahe working for Nugan is compelling and Nugans involvement in Griffith is compellng - you dont even address this, instead going off on a childish tangent; as well as missing the point that Krahe has killed before. As I recall The Prince and The Premier also goes into some detail raising concerns regarding Bazley being the accused, my own concerns regarding the Krahe accusation are drawn from The Prince and The Premier. However that was written unware of the Krahe connection to Nugan and Nugans connection with the Griffith scene.
BUT its been a while since I read The Prince and The Premier, and I dont own a copy, its suggestion that Krahe being named by underworld elements as "too convenient" may have been in regards to the Nielson disappearence not Mackay. Not that you'd bother to check the book for yourself.

So now Frank Nugan has no connection to Griffith? Krahe was not working for him? These men did not form a larger confluence of businessmen, organised crime and police with Robert Askin at its nexus?* Maybe Mackay slipped on a banana peel.

*once again you would know this if you read The Prince and The Premier.

the speculation in The Prince and The Premier that Krahe didn't do it, it was merely being conveniently pinned on him by criminal informants after his death, is in regards to the Nielson murder not Mackay. Forget anything I said regarding him maybe not doing it.
Man I have a shit memory.

What was merely silly before, now descends into the sort of argument favoured by writers on the Knights Templar and such esoterica, where they conjecture "could XXX be explained by YYY?" And a few pages later that conjecture is now regarded as fact, and is the basis of the next conjecture, ZZZ. Look on rense.com for an industry devoted to this style of logic. This form of logic is also known as "Strumian Omnilectics".

Having alleged that Fred Krahe was the murderer of Donald McKay, Jiggens then uses this to tenuously tie Mackay's death as being connected with Frank Nugan, and hints that Nugan actually ordered the hit.

While Nugan most likely had some association with the drug plantations in Griffith, given the known activities of the Nugan-Hand bank, this is more likely to have been as a provider of financial services to the organised crime families of the Calabrian Mafia that were actually running the plantations. Not pulling the strings in a huge operation where Nugan micromanaged every facet, including silencing local trouble-makers like Mackay.

I suppose it is easier for dope smokers to see such connections where legal experts and criminologists can see none.

you quote as the evidence:

and then promptly destroy it:

but the article says:

In early 1977, as the newspapers began calling Griffith the ‘pot capital of Australia’, persistent rumours began circulating that the Nugan Group’s packing plant in Griffith was somehow involved. That year, an independent audit turned up secret accounts in the Nugan Group’s books in the names of local pot growers with cheques for thousands of dollars made out to members of the Trimboli and Sergi families. 

The accounts ran from May 1973 until their discovery in 1977, and they co-incided with Griffith’s marijuana growing years when members of the Trimboli and Sergi families were heavily involved in Griffith’s marijuana trade; members of these families were involved with a thirty-one acre pot plantation at Coleambally in 1975, and with a five acre plot at Euston in March 1977. The secret accounts in their names raised the possibility that some of the pot was being grown for Frank Nugan. Although the Nugans argued that the secret accounts were a way of paying cash to growers of legal crops, such secret accounts would obviously be useful to pay growers for illegal crops.

The gangster tactics that Frank Nugan used to hush up the affair provide further corroboration. When the auditors and independent directors of the Nugan Group tried to find out more, Frank Nugan responded by seeking to remove the auditors, and by intimidating the opposition directors.

The intimidation was impressive. 

The man Frank Nugan hired as his private investigator to look into these matters was Fred Krahe. Four days after the Mackay murder, on the following Tuesday, 19 July 1977, four Nugan Group directors resigned.

Quite a bit more to Nugans dealings and Krahes roll than you would have us believe.
Its a sure bet that if you're a man like Frank Nugan and you hire a man like Fred Krahe as a 'private investigator' then you're looking for some good old fashioned Pinkerton-style headcracking. Why would a purely financial advisor be looking for that?

Again a pithy remark in place of addressing the issue, and again you fiddle with what was said. What was this remark in relation to? Mackay not looking into whatever was going on at the Nugan Group packing plant.
But if anyone still thinks, because they didn't bother to read in any degree of detail instead prefering to troll, that Nugans roll was purely as an advisor then consider this from the third article

(emphasis mine)
Unless those trucks were shipping 10 tones of financial advice, Nugan was directly involved in the business far beyond laundering money.

The first half of this article is uncontroversial summary of John Egan's criminal career, though it has little or nothing to do with Nugan even if Dr Jiggen's wish they had. Moving on...

Strumian Omnilectics again.

Ok, certainly interesting admittedly, but still little more than hearsay. How did he know that he had found minute traces of marijuana? Did he have it tested? While worth investigating, I hope a jury wouldn't find someone guilty on this claim alone. Also Nugan's brother Ken ran Nugan packing, not Frank.

What did Mackay discuss with Ian Salmon about the Nugan accounts?

So Mackay was reluctant to become involved, yet he got whacked anyway.

So a scandal concerning auditing caused 'someone like the truck driver' to suspect that marijuana was the explanation for the auditing issues, then went to Mackay with his theory? Then Nugan learned that Mackay had heard a theory from 'someone like the truck driver' so sent Krahe to terminate him.

I trust that the merit of Jiggen's argument is self-evident.

While Jiggen's makes tenuous conjectures about what Mackay might've known, what we do actually know is that Mackay was actively forcing the issue in the political sphere, building up a groundswell of popular support against the drug plantations. So that the police and NSW government had no excuse to turn a blind eye to what was going on. Don't you think that is the more likely reason that Mackay was killed?

Also, Jiggen's points out that Ken Nugan was in the Liberal Party, yet completely fails to mention the Labor Party membership of high ranking Mafia stooge Al Grassby, and was a Federal Minister no less. Just an oversight I'm sure.

Unless these boys were Cain and Able its fair to say they'd have worked together, or Frank through Ken. Again check The Crimes of Patriots by Jonathn Kwitny, its 1:17am so I'm not exactly going to be tracking down text and footnoting them.