A statutory declaration is a written statement which you sign and declare to be true before an authorised witness. A Justice of the Peace can act as authorised witness to the signing of a statutory declaration.
Statutory declarations are commonly used to legally verify names, addresses, insurance claims, superannuation matters, lost passports and as evidence to support sick leave.
You can find a range of statutory declarations by searching on the sa.gov.au website
If you are wanting a witness for a Commonwealth Statutory declaration under the Commonwealth Statutory Declarations Act 1959 it will need to be witnessed by a person included on the Australian Government's list of authorised witnesses.