La. Code Crim. Proc. art. 415

A. When a vacancy occurs on a grand jury, the court shall fill the vacancy by administering the oath to and seating the first alternate if he is still legally qualified and available, or if he is not, by administering the oath to and seating the second, third, or fourth alternate, if still legally qualified and available, in the order in which the alternates were selected, until the vacancy is filled. If a vacancy occurs and there is no alternate legally qualified and available to fill the vacancy, the vacancy shall be filled by ordering the sheriff or his designee, the clerk or deputy clerk of court, or, in Orleans Parish the jury commissioner, to draw indiscriminately and by lot from the envelope containing the remaining names on the grand jury venire a sufficient number of names to complete the grand jury. If the names in the envelope are exhausted before the grand jury is completed, or if a vacancy occurs on the grand jury and no names remain in the envelope, the court shall order the jury commission to withdraw indiscriminately and by lot from the general venire box or through the use of a properly programmed electronic device as provided in Article 411, an additional number of names sufficient to complete the grand jury.

B. If the foreman of the grand jury is, for any reason, unable to act, the court shall cause a random selection to be made of one person from the remaining members of the impaneled grand jury to serve as acting foreman or to serve as foreman of the grand jury. An acting foreman has the powers and duties of the foreman.