smooth - - I would think that the killer might have preferred that cord as it would be less likely to pick up his DNA if he was tying it barehanded.

Easier movement in a slipknot - - and in bondage that is a factor to consider.

It was a "softer" material than twine or rope. Was he "killing her softly" - or was that cord just convenient, something he had around the house? I don't know. Will be interesting if he ever tells us.