At this point, I think there's at least a 75% chance that Steven Avery is innocent. Most of the further reading I've done has pushed me in this direction.
Teresa was not killed in Steven's bedroom or in his garage. That much is clear. She was probably killed at the quarry and initially burned there (the "secondary burn site"), then brought to Avery's property, perhaps in Teresa's RAV4. To state the obvious, Steven would have to be insane to bring the evidence home to further implicate himself. It's much more likely that was done by someone like Bobby Dassey and/or Scott Tadych.
The defense team has so many mic drop moments during the trial. Jerry Buting is particularly amazing. This interview
with him is essential reading.
Steven's face during the verdict reading is very interesting to me. It doesn't say "damn, I didn't get away with it." Instead it's more like, I can't believe this... how could they get this wrong?... a great injustice has been done... they'll just put me away forever. If he's not innocent of this crime, he certainly in that moment believes he is.