Not a lawyer, but I thought that was only applicable if you suddenly plead the 5th after originally answering questions? From what I know he has always remained silent so I don't think they could do much with that.
You can plead the Fifth in a civil case if you believe that answering the question could subject you to criminal prosecution. But, unlike in a criminal case, where you have an absolute right to remain silent (and it can not be held against you), a judge or jury in a civil case can draw whatever conclusions they wish from your lack of testimony.