It might be difficult to prosecute the passenger for such a breach when all that happened at check in was a question and answer session where the passenger simply lied. What can the check in person do about it?
CASA might be the regulator that makes the rules but the airline is the one who has to try to enforce the rules. At present, passengers only need to lie and then plead ignorance to get away with any breach that is eventually detected.
Perhaps getting passengers to sign a declaration that they understand the dangerous goods questions that SHOULD be asked at check in, and then declare that they are not carrying Lithium batteries in their luggage, might make them think twice about trying to get away with it?
At least with a signed declaration, the airlines and insurance companies might have a better chance of suing for damages? CASA would also have a leg to stand on when it comes to penalising the idiots. Taking a few idiots to court and getting publicity about successful outcomes might help get the message across?