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. An inquiry by John Nagle Q.C. found that "no decent man" could have spread the "scurrilous lies" that Grassby had. 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. He had already lost a civil suit filed by Barbara Mackay, forcing him to unconditionally apologise. Gianfranco Tizzone, who turned informer in 1983, admitted to his 'complicity' in Mackay's murder. Specifically, Tizzone admitted that he arranged for a hit man he knew as 'Fred' to undertake the contract. When shown photographs of possible suspects, Tizzone fingered Bazley as the trigger man. Two years later, hitman James Frederick Bazley was charged over the death. Bazley claimed he was innocent, blaming allegedly corrupt former Sydney detective
Fred Krahe as the killer, 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. Bazley died in 2018. == Legacy ==