What Australian case is this based on?

Scroll down. A bloke mentions... oh what the hell... here, Whannell and Sampson discuss that a bit: http://moveablefest.com/moveable_fest/2014/03/mule-leigh-whannell-angu s-sampson.html

This is my signature. There are many like it, but this one is mine.

http://www.movies.com/movie-news/leigh-whannell-interview-the-mule/17167?wssac=164&wssaffid=news

Movies.com: How close is The Mule to the true story that inspired it?

Whannell: We did base it on a few different things that have happened over the years. There's one story in particular, but I've been told for legal reasons I can't say what it was, but there was one gentleman who held out for quite some time. All of the characters in the movie have been embellished and created, though I must also say that I think the "based on a true story" tag is in some ways a cheeky homage to the Coen brothers and the way they opened Fargo with the crawl "This film is based on true events," and when people do their research, they discover nothing happened. It both is and isn't based on a true story.