I'm curious about the principle of these laws. [Later Edit: not Australian specific, something that can be applied anywhere]

If the only way to convict a suspect would be for them to self incriminate during testimony should the 5th amendment be waived?

How many other rights should be cancelled because they prevent law enforcement from having an easier job?

Banning guns to make doctors' jobs easier is out of the question but banning privacy to make policemen's jobs easier isn't?