I've already heard the spin "They may not have known the shell contained sarin".
CNN tried that spin but their National Security reporter, David ENsor said that although they might not have known the shell contained sarin but it still proved that sarin was indeed in Iraq when Saddam said they had none. Mustard gas traces were found last week. It is showing Iraq had a stockpile.
The spin that they didn't know it had sarin just works in another direction. I think David Ensor of CNN will be looking for a new job soon. He's not playing the game according to script.