Police say the 34-year-old was shot by the older man as he tried to get back into the house.
Trethewey has been charged with two counts of causing grievous bodily harm with intent to murder and is due to appear at a NSW court at a later date.
The Blessings are in a critical but stable condition in hospital.
Speaking to reporters, Superintendent Chris McKenna said Keith Blessing had managed to grab a knife from the kitchen and slash Trethewey during the ordeal.
“He certainly did his best under very difficult circumstances to defend himself and his partner,” McKenna said.
“It was quite impressive, given the extent of the injuries that he suffered.”
McKenna did not comment on whether charges would be pursued in relation to Blessing’s actions, but said people were “entitled to use reasonable force to defend themselves”.
“This [older] male had obviously received quite critical injuries up to that point … but all of these things will form part of our investigation,” he said.
McKenna said nothing had been stolen from the home and Trethewey had a “limited” criminal history.
It is also believed Trethewey was not known to the couple and was not living in Torrington.
The couple were treated at the scene for serious injuries before being flown to Gold Coast Hospital, where they remain in a critical but stable condition.
Trethewey was taken to Armidale Hospital under police guard.
The 34-year-old has since been charged with two counts of cause wounding/grievous bodily harm to person with intent to murder.
Criminal lawyer Sam Macedone said Keith Blessing was “entitled to defend himself” provided there was no proof of “any force that was over-the top”.
“What is important in any self-defence claim is what is going through the mind of that person. The fear they have, and whether they feel they have to do whatever it takes to protect themselves, is how an outsider will decide what is reasonable and what is not,” Macedone said.
“I think if the other bloke wasn’t armed, if he hadn’t been stabbed and given the age differences, then the shooting probably wouldn’t have been justified.
“The fact that he’d already been stabbed by this bloke, who was a lot younger and presumably a lot fitter than him, the fact his wife had already been severely injured, means there would have been enough fear in his mind to do whatever he could to prevent this bloke getting entry again.
“If this bloke is trying to re-enter, you know full well he’s not doing it to give you a hug.”
Rural crime scene
A man named Norm called into local breakfast radio claiming to be a close friend of the couple, saying, under normal circumstances, Keith “wouldn’t hurt a fly”.
“They’re living a peaceful, calm life, up there and some mongrel comes in and does this to him,” he said.
“They put fruit out the front for people to come and get so they can look after their neighbours.”
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