Born in Casino, New South Wales, he studied law at the University of Queensland, and was admitted to the Queensland Bar, entitling him to practise as a barrister, in 1965, becoming a Queen's Counsel and being involved in a number of prominent cases such as the prosecution of High Court judge Lionel Murphy. Widely regarded for his legal abilities, he is also regarded as somewhat of a political and judicial conservative - qualities that may well have made him attractive to the conservative government that appointed him.
Callinan is well-known for his "hobby", writing, having published a number of novels.