I think grand juries are designed to indict suspects on preliminary evidence. If an indictment results, a warrant for arrest is issued. Congress would not be involved in this matter if a US Attorney is involved (i.e., Dept. of Justice =/= Legislature).
OK. But do you agree that "there must be a pending suit in a civil matter or charges filed in a criminal matter before a subpoena can be issued" is completely incorrect?
Subpoenas often come
before someone is charged with a crime.
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To tie this back to the thread, it's certainly possible that the US sent Mt. Gox a subpoena because they were investigating possible wrongdoing, and when the attorney working for Mt. Gox looked into things to try to respond, they came to the realization of "oh shit, Gox doesn't actually have any money!" The investigation leading to the subpoena may or may not have been related to the lack of money, in such a (hypothetical) scenario.
No, I do not agree.
I will graciously concede the argument and admit that I'm wrong if you can show me a rule of court procedure that shows me I'm wrong (no ill-will or ego, here). Until then, I'm going to go with what I know from my own experience as an attorney who practices a fair amount of civil litigation.
I'm also going to go with this theory: there is a federal criminal case pending where the Defendant (XXX) engaged in a fair amount of trading at Mt. Gox and the prosecutors want to discover information related to those trades for their case against XXX.