Ohio Rev. Code § 2939.17
After the grand jury is discharged, the court of common pleas, when necessary, may order the drawing and impaneling of a new grand jury, which shall be summoned and returned as provided by section 2939.03 of the Revised Code and shall be sworn and proceed in the manner provided by sections 2939.06 to 2939.24, inclusive, of the Revised Code. Whenever the governor or general assembly directs the attorney general to conduct any investigation or prosecution, the court of common pleas or any judge thereof, on written request of the attorney general, shall order a special grand jury to be summoned, and such special grand jury may be called and discharge its duties either before, during, or after any session of the regular grand jury, and its proceedings shall be independent of the proceedings of the regular grand jury but of the same force and effect.
Whenever a witness is necessary to a full investigation by the attorney general under this section, or to secure or successfully maintain and conclude a prosecution arising out of any such investigation, the judge of the court of common pleas may grant to such witness immunity from any prosecution based on the testimony or other evidence given by the witness in the course of the investigation or prosecution, other than a prosecution for perjury in giving such testimony or evidence.
R.C. §2939.17