Whatever evidence they had, it was enough to bury what we saw as "reasonable doubt".
What we have to understand, is that the entire defence didn't try to stipulate who instead of Steven was the murderer, that was impossible task. Instead it relied completely on showing that Avery was framed, pointing finger firmly at the law enforcement. Having the only choice between the hick and the sheriffs everyone involved, including media and jury of peers, as a crowd, as a group, as a society, decided to look the other way, disregard any doubts and any potential harm that might be caused to "the nasty hick" in the process, just to maintain status quo.
The true size of the bottomless rift between Avery's and entire Manitowoc filters through the cracks in the documentary by the end - the words of the judge "In terms of assessing your danger to society, the evidence forces me to conclude that you are probably the most dangerous individual ever to set foot in this courtroom" etc. As a viewer you go "how can it be, how sheltered life have you guys had in that county?" But try and understand - it is all happening in one county, effectively everyone already heard, met, came across or has an opinion on the guy, whether they believe the evidence or not. And that's how they see him. Media hates him. Sheriff muse about killiing him. Dassey's defence lawyers actively participate in trying to nail him. Maybe the idea that Avery clan nearly became the "Dynasty" magnates of the hood had something to do with it as well, maybe the fear of another lawsuit turning "those people" into millionaires, we will never know.
anticonscience asked if I think he's guilty. I don't care to be honest. If he was guilty, what was done to him was a crime. If he was not guilty, what was done to him was a crime. I'm fascinated by the mechanics of witch hunt society that was caught so red handed by this documentary and outed in public. And then I ask myself - we all encountered these types of neighbours and people in community, where you just quietly think at some point if it wouldn't be better for everyone if something just serendipitously happened to them - an earthquake, a thunder from skies, a plague of bedbugs at least. I know I have. And they were nowhere near as bad or dangerous as Avery's. No crimes of that calibre were involved. So, here it is - the society that was given the earthquake and plague stick to operate with, they can use it on that bad neighbour. The people who are willing to sweep under the carpet that operator call where the Sgt names the vehicle when given registration plate, and that opened vial, and will believe in a story of chaining and slicing with no blood and no DNA etc, etc. Just to get rid of the that tree branch. Working together to cut that blood line.