About 1970 there was a case between NSW and Victoria. A chap in Victoria
(Reid or Read) )took a gun and shot someone fishing on the Murray river
bank, in order to steal his car.
He was charged and convicted by Victoria with murder. The accused appealed,
and argued that Victoria had no jurisdiction because the murder took place
in NSW (where he would be able to negotiate a lesser sentence due to
differences in state laws). So the entire case pinned on the exact location
of the border.
When NSW ceded Victoria, it kept the Murray river, so as not to lose toll
revenue from steamboats which at that time (1840s/50s) were the mainstay of
transport.
Thus the border was defined as the top of the left (ie south) bank.
The accused argued that the butt of the gun was in Victoria and the barrel
in NSW when he shot the guy, and the victim was entirely in NSW (the
fisherman was standing on the water's edge on the southern bank, the
accused at the top of the bank behind him).

He won his case( that Victoria had no jurisdiction) was extradicted to NSW
and the Victorian conviction for murder was upheld.

The cases are Reid v R, and R v Reid, and are in the Australian law
journals/reporters, c.1970-74.