Judge William Duffin:

Most significantly, however, the (state) court of appeals erred when it focused on the statements of the investigators in isolation to conclude that they did not make any promises of leniency. True, no single statement by the investigators, if viewed in isolation, rendered Dassey's statement involuntary. But when assessed collectively and cumulatively, as voluntariness must be assessed, it is clear how the investigators' actions amounted to deceptive interrogation tactics that overbore Dassey's free will.

Conviction Against Brendan Dassey of 'Making a Murderer' Is Overturned https://t.co/L9BB5dRDdD — Making A Murderer (@MakingAMurderer) August 13, 2016

Update (9/12): Brendan Dassey will not be released yet, as the Wisconsin AG is appealing his overturned conviction.

The documentary focused on the conduct of law enforcement involved with the case, and while it does not appear to have impacted the judge's decision, his ruling reflects similar concerns. According to Judge Duffin, state courts were in error by deciding that investigators never made promises to Dassey. Now, the state can decide to retry him, appeal, or it will have to release him within 90 days.