This paper examines true crime documentary mini-series Making a Murderer and The Staircase within the context of their snowball transmedia structure. While their success partly rests upon the spreadable features of streaming platforms, they also owe a great deal to the community activities of dedicated fans on a variety of third-party platforms and social media networks.  Consequently, the narrative closure of true crime streaming mini-series and limited-series merely offers an opportunity for further narrative encounters via transmedia user-generated seriality. This amateur transmedia structure prompts reconsideration of forces that undermine the boundaries of the streaming mini-series in the digital age.