Here is what RJ said - Edit 1
Before modification by darius_sedai at 28/05/2010 03:33:17 PM
But there are actually no clues regarding Graendal in the first 4 books, since Graendal isn't even really mentioned there.
RJ has never implied that there are clues in the first four books as to who killed Asmodean. Why on earth would there be? Asmodean was only captured in book 4. Is Graendal supposed to be thinking about killing Asmodean in book 1 while Rand is drinking from the Eye of the World? That's crazy stuff.
Book 5 established four Forsaken of principle importance (apart from Moghedien who had an altercation with Nynaeve). They were Lanfear, Rahvin, Sammael and Graendal. Lanfear and Rahvin died, and that left Sammael and Graendal as the principle murderers. RJ then provides several conversations where they discuss Asmodean. That's real evidence. What's Slayer got... the statement that he's the Shadow's assassin? Does that mean he killed Adeleas and Tylin too? C'mon.
In a 2003 CoT book tour interview:
He also said that the guy used only clues that were available in the first five books to do it. He then thought for a moment and said he may have used one or two things from later books.
Logically that really only means TSR and TFoH and maybe LoC and TPoD would contain clues since Asmodean didn't even appear until TSR I find it hard to believe RJ would have planted clues to a death before a character even appeared in the series!