Public interest defence in the apartheid era
During the apartheid era, there were one or two cases where journalists or activists attempted to raise a "public interest" type defence to criminal charges instituted under prevailing security and information legislation. They did this by attempting to extend the criminal law notion of "private defence" (where a person's allegedly criminal conduct is deemed lawful because they were acting in defence of themselves or a third party) to instances where information was accessed or released in the public interest.
Defences were not dismissed outright
These cases were ultimately determined on other grounds, but the defences were certainly not dismissed outright - in one case the then Chief Justice, Corbett CJ, held as follows: "The defence had sufficient substance to merit ... serious consideration ... "
Notwithstanding the very oppressive information and secrecy regime under the apartheid government, the courts still occasionally emphasised the importance of media freedom. In one case in which a journalist was detained under the Public Security Act for refusing to disclose his source, the court held in his favour and stated the following:
"The right of members of the public to criticise, even in scathing terms, the action of a government ... is one of the cornerstones of democracy."
Of course, these sorts of rulings were the exception.