Parrot, sorry if I missed it...but what is your theory on how this all went down?
I don't really have a full theory, I'm just taking things over the hurdles as they come.
Off the cuff; I believe it's possible he killed her in the garage and way too much is being assumed about how much spatter and gore there would be from a .22. I'm saying not that much.
I think the bleach on Brendan's pants and his statement (to his mother, not leading detectives) that it came from helping Steven clean his garage was huge. It would be possible to clean it to a level where something might be missed by the Keystone cops on this case. Or maybe he killed her somewhere else and brought her back. Early on Brendan says Steven told him he tied her up and stabbed her in her car. I think that could possibly be true. I do think he probably burned her there in the burn pit.
I think he probably killed her because of the circumstances of how she was brought there and the amount of evidence that surrounds Steven Avery is pretty substantial. I'm an Occam's Razor guy and generally not a big fan of conspiracy and/or frame-up theories and that's especially true in this case where things would have had to have been done just so. It would be incredibly fortuitous, or prescient, for someone to kill someone and burn the body and frame Steven Avery on the very night he decides to have a bonfire.
Not that I believe everything the police and prosecution say. The two completely different versions presented in the two trials troubles me deeply. I find the discovery of the key really strange as well, but not strange enough that I feel compelled to think it must have been planted.