In the case of Brendan Horan and his expulsion from the New Zealand First caucus, Winston Peters yesterday cast himself in what for him are the unfamiliar roles of judge, jury and executioner.
For someone who would normally fight to the very death for someone's right to natural justice and "due process", the swift exorcism of Horan was Peters seemingly behaving very much out of character.
What the public has not witnessed is Peters' two-month-long struggle to get any kind of explanation from Horan as to why allegations he had misappropriated money belonging to his mother were false and malicious.
For Peters, loyalty is very much a two-way street. Few leaders are as generous in terms of loyalty to his troops as he is. An MP stuck in the mess Horan finds himself in could normally expect to enjoy Peters' backing until his or her claim of innocence is resolved one way or the other. But Peters had to move quickly for the party's sake.
The allegation that one of NZ First's MPs was stealing money from his elderly mother was something that went to the core of the party's reliance on superannuitants as a voter catchment.
In recent days, Peters received "substantive information" dealing with the Horan family's dispute, which is understood to have included financial and other records.
As a result, certain things are said to have fallen into place.
For Peters - a stickler for evidence in document form - there seems to have been enough to persuade him that he could no longer have confidence in Horan.
Hence, Horan's expulsion from the caucus by unanimous vote - and inevitable expulsion from the party, something that requires the say-so of the board of NZ First.
Peters was so sure of his ground he did not even read Horan's press release yesterday denying any suggestion he had stolen from his mother or misappropriated her money and assets, and expressing confidence any "proper" investigation would exonerate him entirely.
Horan's expulsion is not without risk for NZ First. As an independent MP, Horan could be a nuisance for Peters and his party - at least temporarily. There will be no longer-term damage to the party from this affair.
Horan says he is going to stay in Parliament. He has no mandate for doing so. He is only there because of Peters' ability to pull votes. Horan should now do the proper thing and resign from Parliament altogether.