This article explores the often fraught intersections between social media, fair trial principles and community engagement with high-profile crimes. Specifically, a detailed analysis is undertaken of the Facebook response to the arrest of Adrian Ernest Bayley for the murder of Ms Gillian (Jill) Meagher in Victoria, Australia in 2012. As one of the first Australian crimes to receive a significant social media response, this research provides empirical insights into the dynamic and evolving relationship between social media, the community and criminal trials. By drawing on a critical discourse analysis of over 3,000 comments on the R.I.P Jill Meagher Facebook page, this article identifies and critiques a 'Discourse of Challenge' in which digital communication enabled the reinterpretation of legal principles. Further, this article provides empirical insights into the meaning-making processes of Facebook discourses and focuses on how fair trial principles are contested on Facebook in novel and, at times, contradictory, ways.