Gonzales Aide to Invoke Fifth Amendment

From what I understand, the 5th amendment is in regards to criminal trials. Here is the relevant section:
"nor shall be compelled in any criminal case to be a witness against himself"

Testifying before Congress is NOT a criminal case. This is an investigation. It's the same as if a drug dealer refused to talk to the police for fear of prosecution.

One thing that is certain... if she is refusing to give testimony on the grounds of the 5th amendment, then she is saying that she is guilty and just doesn't want to get caught.