Earlier, Mr MacDonald's wife told the court that her husband threatened to kill an osteopath he claimed had ruined his life by making a back injury worse.
Rowena MacDonald said Mr MacDonald made the threat weeks before allegedly shooting and seriously injuring the man, John MacKenzie, and his wife Fay.
Mr MacDonald is accused of attempting to murder the couple at a property in Dornie, Wester Ross, and attempting to murder his wife at their home in Tarskavaig on Skye.
Mrs MacDonald was giving evidence for a second day having earlier told the jury that her husband had left her drenched in blood after attacking her in front of their children as he suspected she was having an affair.
She told the court Mr MacDonald, a marine engineer, was on sick leave after suffering a back injury in spring 2022 when he visited osteopath Mr MacKenzie.
She said her husband was "very, very upset" for a long time afterwards and wanted to sue Mr MacKenzie, claiming the treatment had made his injury worse.
Mrs MacDonald told the court: "He would say I'm going to kill him, I’m going to bloody kill him for ruining my life".
She described her husband as being "quite a ranty person" and that at the time said she had thought it was just talk.
Mrs MacDonald was also asked about a physical altercation between her husband and Mr MacKinnon in 2013 - nine years before he is accused of murdering him.
She said she was eight months pregnant at the time and was hiding in the bathroom, from where she could hear a commotion.
She told the court that when her husband came back into the house afterwards he was angry and breathless "with some sort of facial cut".