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.

[0] https://en.wikipedia.org/wiki/Death_of_John_O%27Keefe