Is this a legit legit legal defense?

In Australia there was a local new story about a man who was wrongly double-billed by his phone network provider, instead of receiving his usual monthly of bill of $90 he instead received a $180 bill.

He immediately visited his phone store, started screaming at a staff member then got violent and stabbed him to death.

He's currently yin police custody and his lawyer is formulating a defense citing that he was "under intense psychological pressure in his personal life, his finances are very tight and this oversight pushed him over the edge, he suffered from acute insanity but is now remorseful" The lawyer is citing the double-bill and the tense finances of his client as the crux of his defense.

Your thoughts, is this justified?
7 mo
sorry, forgot to include a recent update

he was acquitted and placed on a good behavior bond and the court mandated he undergo psychological evaluation
Is this a legit legit legal defense?
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