"Hands clenched, just this look of evil. I've seen him pissed off but not like [that]. He just came at me," the defendant said.
He said he noticed Bacon was holding scissors and swung the bat to ward him off.
"I thought he was going to stab me."
It was the first time Collins had mentioned the scissors, something Crown prosecutor Richard Smith picked up on during cross-examination.
Why had it only arisen now, he asked.
Collins, who gave a two-hour police interview a couple of weeks after the incident in which he neglected to mention it, said he had forgotten the detail.
"Are you asking this jury to believe that you're in an interview for murder and you didn't remember that at the time of the incident he had scissors in his hand?" asked Mr Smith.
"I tried to block a lot of it out," Collins said.
The defendant said his first blow — "like an axe swing" — knocked the victim to his hands and knees.
Bacon allegedly said: "I'm going to f ... ing kill you ...''
Then Collins said he delivered another blow, this time to the side of the head.
"He kind of toppled over to the side, falling on to his back and I just instinctively followed through and hit him a third time," he said.
"I would've been 99 per cent sure he would've been dead ... It seemed like there was blood everywhere."
Collins said the cricket bat – which he used for protection – had been propped against a couch, as he returned from the kitchen from making a hot drink, when Bacon advanced on him.
He accepted Smith's assertion that it was a "remarkable stroke of luck" that the weapon was immediately to hand when he needed it.
Under cross-examination, Collins denied he was jealous of Bacon's close relationship with his partner, 32-year-old Aleisha Dawson, whom he said was seated on a couch during the violence.
He admitted having earlier threatened to punch the victim but could not recall the reason why.
Medical witnesses gave evidence of breaks to three of the victim's fingers.
Smith suggested that had been because Bacon raised his hands to parry the blows being aimed at his head.
Collins denied that was the case.
The breaks could have been from him standing on the victim's hands in the aftermath, the defendant said.
So how was Bacon's thumbprint in blood found on the cricket bat? It may have touched the surface when he was moving the body, Collins explained.
The defendant accepted the contents of his police statement and his account in court differed significantly.
He put that down to the fact he had been smoking a lot of methamphetamine after the killing.
"You're coming up with a story to fit the evidence. That's what explains all these changes in your story," Smith said.
Collins denied that was the case.
The court heard earlier about an incident in June 2018 in which Bacon assaulted his ex-partner, something of which Collins was aware.
However, he confirmed yesterday the victim was not someone he feared.
Collins and Dawson bundled the body into a sleeping bag, drove from the Lock St scene in Bacon's Toyota Emina and dumped his body beside a gravel road 35km north of Dunedin before they continued up the South Island.
The defendant said he concealed the corpse simply because he "panicked".
Smith had an alternative theory.
"Anyone who saw his injuries would have known it was murder."
The couple were found and arrested by police in Rotorua on February 20.
Both prosecution and defence will close their respective cases on Monday.
