Why should provocation be a defence rather than something the judge should take into account in mitigation?

Because self defence is not the only situation where a person is morally justified in using force, even lethal force against someone who has wronged them terribly. Lets consider an example.

If Henk Bouma had been able to free himself to attack Poumako and his henchmen while they were leaving his Reporoa farmhouse no legal system with any respect for normal human emotions should convict him of a wrong. They tied Bouma up, took his wife Beverly to suffer for hours in another room, taunted Henk, then shot her dead.

Self defence would not be available to someone in Henk’s position if he attacked the home invaders as they were leaving, because they were clearly then ending their threat.

If only the facts had played out as proposed in this thought experiment! He would have deserved commendation, not conviction.

Another comment asked why I linked Weatherston’s excuse for killing Sophie with the ‘homosexual advance’ defence. I thought it was obvious. It is the same defence – the argument that the irritation provoked by the victim’s express or implicit insult to the killer justified their subsequent reaction, or drove them into a state in which they should not be held responsibe for their actions.

Often the homosexual advance excuse merges with a self defence claim (‘homosexual panic’). Weatherstone’s excuse tries this trick too, with the ‘scissor attack’ story.

Without solid evidence of reason for panic the law should treat the homosexual advance defence with derision, like Weatherstone’s defence.

[Update – Guilty for Weatherston has saved the law from an explosion of outrage. Instead there is the heightened rumble of discontent.

When it dies down a little provocation can be treated more dispassionately. But whatever emerges, the law must recognise and not consistently affront the consciences and emotions of the ordinary people without whose support it will decay.

The criminal law is the consensus on minimum morality in action. Morality is very interested in questions like – who started it?. What did he/she deserve? We are evolutionarily conditioned to find those matters vital.  If judges apply mumsy rules, like "nothing excuses violence"  or "I dont care who started it, you joined in" they are not judging, The are just applying a rule, which could be done by a computer, or the police, (assuming the evidence is clear).

From this case the judges should take a lesson, and simplify the defence of provocation. It should only relate to what would provoke ordinary reasonable people, not drunks or P addicts or nut cases, or homophobes. The judges should now punish those who turn it into mockery.

From other cases they should accept that ordinary people want the law to distinguish between those who start fights or cause trouble, and those who respond even if their response is "disproportionate".  The criminal should bear the risk of significant  disproportionality in the response to thuggery, rape or robbery , even if common sense says the defence can only go so far.]