Traditionally, the grand jury has conducted its work in secret. Secrecy prevents those under scrutiny from fleeing or importuning the grand jurors, encourages full disclosure by witnesses, and protects the innocent from unwarranted prosecution, among other things. The long-established rule of grand jury secrecy is enshrined in Federal Rule of Criminal Procedure 6(e), which provides that government attorneys and the jurors themselves, among others, ﷿must not disclose a matter occurring before the grand jury.﷿Accordingly, as a general matter, persons and entities external to the grand jury process are precluded from obtaining transcripts of grand jury testimony or other documents or information that would reveal what took place in the proceedings, even if the grand jury has concluded its work and even if the information is sought pursuant to otherwise-valid legal processes. At times, the rule of grand jury secrecy has come into tension with Congress' power of inquiry when an arm of the legislative branch has sought protected materials pursuant to its oversight function. For instance, some courts have determined that the information barrier established in Rule 6(e) extends to congressional inquiries, observing that the Rule contains no reservations for congressional access to grand jury materials that would otherwise remain secret. Nevertheless, the rule of grand jury secrecy is subject to a number of exceptions, both codified and judicially crafted, that permit grand jury information to be disclosed in certain circumstances (usually only with prior judicial authorization). Perhaps the most significant of these for congressional purposes are (1) the exception that allows a court to authorize disclosure of grand jury matters ﷿preliminarily to or in connection with a judicial proceeding,﷿ and (2) the exception, recognized by a few courts, that allows a court to authorize disclosure of grand jury matters in special or exceptional circumstances. In turn, some courts have determined that one or both of these exceptions applies to congressional requests for grand jury materials in the context of impeachment proceedings, though there is authority to the contrary. Additionally, because Rule 6(e) covers only ﷿matters occurring before the grand jury, courts have recognized that documents and information are not independently insulated from disclosure merely because they happen to have been presented to, or considered by, a grand jury. As such, even if Rule 6(e) generally limits congressional access to grand jury information, Congress has a number of tools at its disposal to seek materials connected to a grand jury investigation. Prior Congresses have considered legislation that would have expressly permitted a court to authorize disclosure of grand jury matters to congressional committees on a showing of substantial need. However, in response to such proposals, the executive branch has voiced concerns that the legislation would raise due-process and separation-of-powers issues and potentially undermine the proper functioning of federal grand juries. These concerns may have resulted in Congress declining to alter Rule 6(e). As a result, to the extent Rule 6(e) constrains Congress' ability to conduct oversight, legislation seeking to amend the rules governing grand jury secrecy in a way that would give Congress independent access to grand jury materials may raise additional legal and pragmatic issues for the legislative branch to consider.

You'll find extensive discussion of the composition and conduct of the grand jury, joint defense agreements, evidentiary issues, grand jury secrecy, and many other constitutional issues.