In what way is Serah responsible for Laguna's death? She voted for Galuf, and vote-hopped to avoid being in on the killing vote. That's a townie strategy.
As I've said, no, it's not much to go on, but it's all I've got at the moment.
Point: Why didn't Laguna protect himself? What did he know that we don't?
At this point, I think Wedge's attempt to throw suspicion on Serah is more suspicious than Cid's maybe-roleclaim.
##Unvote: Cid
##Vote: Wedge