Cook said he was stopping Fraser from closing the door and trying to prevent her from putting the keys in the ignition with his left hand, while holding the wheelbrace in his right when Hancock began "kicking the bloody life out of me".
He said Hancock then wrenched the wheelbrace from him and struck him over the head with it, causing a large gash.
Under cross-examination, Cook denied giving Fraser permission to change the ownership details of the vehicle.
Hancock said she had acted in self-defence. Cook was raising the wheelbrace, trying to strike Fraser and she wrenched it off him.
Cook was enraged and was advancing on her so she instinctively hit him with the tool.
"It was totally self-defence. I feared for my life and Alison's life. I thought I was going to see my friend's brains scattered over the windscreen," she said.
Fraser said Cook had gifted her the vehicle and he had no rights to it.
She said she had no doubt that Cook would have split her head open had Hancock not blocked a blow with the wheelbrace and then turned the tyre iron on him.
Judge O'Driscoll said that when a defence of self-defence had been raised the onus was on the prosecution to exclude it beyond a reasonable doubt and they had not managed to do so.
Cook will defend assault charges in February.
- The Greymouth Star