Looks like Eyre Peninsula....??

We don't have a Fifth. What we do have is what we borrowed from the Brits. When a person is suspected of committing an offence a police officer questioning the individual must caution that individual that they don't have to answer questions. If the police officer doesn't do that then a court is very likely to throw out the evidence of the interview from the point where the caution should have been administered. This is done in the absence of a jury, it's called a voir dire hearing.

In court there is a common law right to protect oneself against self-incrimination.

__________________
"There were no D-Day Heroes in 1973" - Cold Chisel Khe Sanh