Where an indictment has been returned against an individual, it is axiomatic that someone must have provided testimony before the Grand Jury in support of the probable cause determination rendered thereby. A Government agent may have summarized the results of his investigation or third party witnesses may have testified. Here again, Rule 16 seeks to protect the identities of these persons from pre-trial disclosure. Although a defendant may discover a transcript of his own recorded testimony before a Grand Jury, if in fact he testified before them, subsection (a)(2) protects from pre-trial disclosure all other transcripts. Only if a defendant demonstrates a “particularized need” for such disclosure will a defendant be granted pre-trial access to Grand Jury testimony. Even here, however, a defendant must carry a heavy burden in demonstrating that such disclosure is absolutely vital to the preparation of a factual or legal defense.