I just read this post on the main Reddit page: http://prorev.com/2009/07/court-discovers-sixth-amendment.html . Basically it's about a person who got off of conviction because the witness against him didn't appear in court. Here is a quote from the article:

"The reversals hinge on an important constitutional issue stemming from eight words tucked in the Sixth Amendment known as the Confrontation Clause. In all criminal prosecutions, the accused has the right "to be confronted with the witnesses against him."

Has this right been explicitly removed for rape trials?