CNET has a decent article on this. The special master is an unpaid agent of the court (usually a retired judge or law professor) who are not related to the case

CNET has a decent article on this. The special master is an unpaid agent of the court (usually a retired judge or law professor) who are not related to the case at hand. In this case, the special master will examine Chen's possessions for evidence related to the stolen iPhone and forward only that information to the presiding judge. Chen gets an opportunity to object to the gathered materials. Only whe that is done will the judge decide what the DA gets to have for his or her case. (paraphrased from http://news.cnet.com/8301-13579_3-20006876-37.html http://news.cnet.com/8301-13579_3-20006876-37.html)