A challenge to an individual grand juror may be interposed by either party, for one or more of the following causes only:
1. That he is a minor.
2. That he is not a qualified elector.
3. That he is otherwise disqualified under any of the provisions of law, in relation to the qualification of grand jurors. 4. That he is insane.
5. That he is a prosecutor upon a charge against the defendant.
6. That he is a witness on the part of the prosecution and has been served with process by an undertaking as such.
7. That a state of mind exists on his part in reference to the case, or to either party, which will prevent him from acting impartially and without prejudice to the substantial rights of the party challenging; but no person shall be disqualified as a grand juror, by reason of having formed and expressed an opinion upon the matter or cause to be submitted to such jury, founded upon public rumor, statements in public journals, or common notoriety, provided it satisfactorily appear to the court, upon his declaration, under oath, or otherwise, that he can and will, notwithstanding such opinion, act impartially and fairly upon the matters to be submitted to him.
R.L.1910, § 5700.