Federal Grand Jury

What is the name of your state?Federal
Just a question for anyone familar with Federal Criminal Procedure/Constitutional Law. There is a current indictment of two people for fraud claims. Another man, involved, testified against the two men indicted in exchange for a plea bargain. He now claims that he did not understand what the grand jury meant and its use and is going to back out on the plea bargain. My question is this-can the man who testified at the grand jury be forced to testify at the trial of the two men who were indicted? Or would that violate his 5th Amendment right not to incriminate himself. At the grand jury, the man did waive his 5th Amendment rights but I am not sure if this only applies to the grand jury but also to subsequent proceedings? Anyone with a possible answer would be a great help. Also if the man refuses to testify against the other two, could he be indicted and tried for obstruction of justice?

[JETX]

"My question is this-can the man who testified at the grand jury be forced to testify at the trial of the two men who were indicted?"
Yes. He can be forced to appear under subpoena, and unless he invokes his fifth amendment rights, can be forced to testify under threat of contempt. Further, if he refuses to testify, his plea deal will be revoked. Finally, if he has already testified at the grand jury, that testimony can be used in court if needed.

"Or would that violate his 5th Amendment right not to incriminate himself."
Depends on his claim.... and his deal.

"At the grand jury, the man did waive his 5th Amendment rights but I am not sure if this only applies to the grand jury but also to subsequent proceedings?"
Again, as noted above, if he has already testified at the grand jury, his statements are already on record. They can simply be read into the new trial.

"Also if the man refuses to testify against the other two, could he be indicted and tried for obstruction of justice?"
Possibly, depending on a full review of the facts. Plus as noted above, his plea deal would be withdrawn and the charges prosecuted, very likely aggressively.