I just finished Bryson's "A Walk in the Woods" in which he spends some time discussing murders which have occurred on the Appalachian Trail. My impression is that this trail is more dangerous than the PCT in that when they developed the AT they were unable to secure a broad swath separating the trail from "civilization". In general, the AT is not as remote as the PCT and so one is more likely to run into undesirable "non-hikers". Even so, the murders on that trail as still small in number and you no doubt have a bigger chance of getting hurt while driving to the trail.