They are referring to how there’s a belief in some parts of Massachusetts that the police are trying to frame Karen Reid for the death of John O Keefe (0). At its climax it was all over the news, it was discussed at a lot of water coolers, and there were even billboards bought by the highway to show support and draw attention to the court case.
The amount of evidence described in the Wikipedia entry that relies on mobile data is both fascinating and jarring; step counts, battery temperature, automobile software, Ring cameras...wow.
[0] https://en.wikipedia.org/wiki/Death_of_John_O%27Keefe