[3] In 1974, Mackay stood as a Liberal candidate for the House of Representatives against Al Grassby in the electorate of Riverina.

Concerned about the growing illegal drug trade in his local area, and learning of a large crop of marijuana in nearby Coleambally, Mackay informed Sydney drug squad detectives, resulting in several arrests and the conviction of four men of Italian descent.

[10] Mackay's disappearance made headlines around the nation and many, such as Griffith supervisor of detectives James Bindon, drew the conclusion that Trimbole was responsible for the apparent contract killing.

In 1979, Woodward found that Mackay had been murdered by a hitman acting on instructions from the "Honoured Society", a Griffith-based cell of the 'Ndrangheta, a Calabrian criminal organisation.

[16] In 1980, Grassby was charged with criminal defamation when it was alleged that he had asked state politician Michael Maher to read in the New South Wales Legislative Assembly a document that imputed Mackay's wife Barbara and her family solicitor were responsible for Mackay's disappearance.

[17] Grassby maintained his innocence and fought a twelve-year battle in the courts before he was eventually acquitted on appeal in August 1992 and was awarded A$180,000 in costs.

[23] Bazley claimed he was innocent, blaming allegedly corrupt former Sydney detective Fred Krahe as the killer,[24] but was convicted of conspiring with Tizzone, Trimbole, Joseph and unknown other persons to murder Mackay, as well as the murders of drug couriers Douglas and Isabel Wilson.

[22] In July 2012, 35 years after his disappearance, the New South Wales police offered a $200,000 reward for information on the whereabouts of Mackay.

[26] The Churchill Trust awards a Donald Mackay fellowship annually for journalists and detectives to study methods of investigating and bringing to light organised crime.

[17][28] The statue of Mackay itself is a white marble bust with a plaque inscribed with "All that is necessary for the triumph of evil is for good men to do nothing."