I would have sworn that in one class I attended, where Harold Fish was a topic of discussion, the point was made that one of Fish's bases for appeal was that the man he shot had a past pattern of behavior that exactly matched what Fish described as having been displayed toward him.
In the original trial, the defense was not allowed to prevent that evidence.
The instructor of the class I attended said that was a specific point on which the appellate court said the trial judge had erred. Because the past pattern of behavior matched so perfectly with what Fish had described to investigators, it should have been allowed to support Fish's veracity.
It's entirely possible the instructor of the class was in error, but this is what he told us.