Who is Charles Nesson from A Civil Action and what is their importance?

Nesson is a Harvard law professor who eventually joins the Schlichtmann team in the Woburn case. Charlie is a bright, creative individual who sees this case as a landmark one against corporations which pollute with impunity. He encourages Schlichtmann's aggressiveness against the defendants and, in one instance, is able to determine the fallacy of mathematical calculations of an expert witness for the defense.