Interesting question

Posted on: September 13, 2019 at 21:25:25 CT

A person can be prosecuted for perjury if he or she testifies X in the grand jury and then testifies Y in a subsequent trial. The grand jury testimony is available to prosecutors for that purpose.

However, if a person testifies X happened before a grand jury, that grand jury testimony can not be used at trial to establish that X happened. The person has to be called as a witness and asked the same questions he or she was asked before the grand jury.

But there are clear limitations on the scope of the use of grand jury testimony in a subsequent trial.

The subpoena power typically doesn't come up because the prosecution in a grand jury proceeding is the same prosecution at trial. I.e. the Boone County prosecrutor calls a grand jury, takes testimony for a witness and then calls the witness at trial.

Here the testimony was presented to a grand jury, part of the judicial branch, and now the Congress wants to use the testimony in a Congressional proceeding. Again, it can call the witnesses and ask them the same quesations they were asked in the grand jury. It just can't use that testimony without calling the witnesses in its own proceeding.