I honestly think it depends on how you view the case. I think Avery is guilty and I can see where the documentary is biased with things like skipping over (or omitting) some of his unsavory past antics. I watched this with my husband, who thinks Avery is innocent and the documentary was balanced.
Bottom line though both need a new trial. And although I think Steven Avery was involved, on the evidence the state has he should be found not guilty. The only one I feel so sorry for is Brendan Dassey - and the victim of course.