Dede's attorney is mincing words. From anything I can read an investigative Grand Jury investigates organized crime and improper conduct of public officials in some states. Not criminal cases. We need an attorney to weigh in here.
DeDe's testimony could have been brief if she asserted her rights under the 5th amendment. THEORY.
This is the tricky part.
What is a grant of immunity?
A grant of immunity to a grand jury witness overcomes the witness's privilege against self-incrimination, and the witness is then required to testify. The prosecutor is prohibited from using that testimony or leads from it to bring charges against the witness. If a subsequent prosecution is brought, the prosecutor bears the burden of proving that all of its evidence was obtained independent of the immunized testimony. In practice, it is difficult to successfully prosecute someone for criminal activity they discussed in immunized testimony unless the prosecution had a fully prepared case before immunity was granted.
Many states grant the witness "transactional immunity," barring prosecution for a transaction discussed in the immunized testimony regardless of whether there are independent sources of evidence.
I am of the opinion this is a true Grand Jury collecting evidence and "Investigating" to determine whether there is probably cause to indict.
http://www.abanet.org/media/faqjury.html