The man who murdered a so-called good samaritan in Auckland in 2008 was already a convicted killer.
In the High Court at Auckland on Monday, Pauesi Leofa Brown admitted murdering Austin Hemmings, who went to the defence of Diane Nonu in central Auckland in 2008.
Mr Hemmings, 44, was stabbed to death with a 20cm kitchen knife when he intervened in a domestic dispute between Brown and Ms Nonu.
Crown prosecutor Kevin Glubb says Brown, 47, was charged with murder in Australia for stabbing and killing his estranged girlfriend in 1992.
But the following year, a jury accepted his defence of provocation and he was found guilty of manslaughter.
Mr Glubb says Brown's previous convictions in New Zealand included three other knife attacks.
He is due to be sentenced on 10 December.