So Gabaldon asked Martin how things were going with “the newest book.” Quoth Martin, via Gabaldon:
I’m having all kinds of trouble. Have you ever killed somebody off that you later realized that you needed?…I just painted myself into a corner.
Let’s note that we don’t know when Martin and Gabaldon had this conversation. Perhaps it was years ago, and Martin has already written himself out of whatever corner he’d painted himself into. In any case, you have to wonder which dead character was/is giving him problems. It’s probably not a major one — the deaths of characters like Ned and Robb and Tywin are woven into the narrative such that we can’t imagine Martin ruing killing them off. Maybe someone like Maester Aemon or Qyentyn Martell or Kevan Lannister? It’s not the series lacks for dead people.
The idea of Martin being tripped up by a dead character he “needed” rings true. Martin is meticulous about his plotting, and has been known to rewrite parts of his books after he decides to change something. Diana Gabaldon isn’t phased, though. “This happens all the time when you write,” she says. “But you have an imagination…So if you paint yourself into the corner, I said, what you do is you get a new bucket of paint and you paint yourself back out and do the floor behind you. I mean, you can revise history — it’s easy if you try.”
Outlander – George R.R. Martin – The Winds of Winter –