BBM - You're a hoot! I expect you're right about Nel. However, regardless of how hard Nel squeezed, I don't believe he would have gotten anymore than "I don't know. I was asleep." And upon waking up "I didn't hear anything."
Surely they could have asked him about how the two of them were generally and did he hear or see anything of an argument previously. He could have been called as a character witness for the defence even, but no niente!