One of the long-standing legal principles has been that a wife or husband cannot (at least as I understood it) be compelled to give evidence against the other. The Australian High Court appears to have overturned this understanding, at least so far as Australia is concerned. Decision here.
On the surface, this is quite a significant decision. Hopefully one of my legal blogging colleagues (Legal Eagle?) will elucidate all this.
Legal Eagle has now discusses this case in Spousal right to silence abolished in Australia'