President Clinton was sworn in by a prosecutor (if what
you've heard is true, and I suspect it is), it was because he was not testifying before
the grand jury but at a distance, with his testimony being relayed via video transmission.
Since the grand jurors were not physically in the same place as the President, I assume
the prosecutors decided that one of them would have to administer the oath. . . on the
assumption, no doubt, that the oath would have to be administered by someone who was in
the same room as the president.
This would be a clear violation of Rule 6(c). I'm not
aware of this ever having come up before, probably because witnesses normally testify
before a grand jury and are, therefore, sworn in by a foreperson or deputy foreperson. I
do not think the error would have any serious legal consequences, since the U.S. Supreme
Court has applied the doctrine of "harmless error" to grand jury proceedings.
This means that if an error, like having a witness incorrectly sworn in, occurs during a
grand jury proceeding, courts will not order any kind of remedial action if the error was
"harmless," i.e., if it did not prejudice the object of the grand jury inquiry.
To be harmless, a court must be able to say, with some confidence, that an error did not
influence a grand jury's action, which is usually to indict someone. Since the President
has not been indicted, I assume the test here would be whether the error in swearing him
in caused the grand jury to issue a report to the House Judiciary Committee when it would
not have done so if he had been correctly sworn in. And it seems to me that the answer to
that question has to be that the error was harmless.