Ohio Rev. Code § 2939.10
The prosecuting attorney or assistant prosecuting attorney may at all times appear before the grand jury to give information relative to a matter cognizable by it, or advice upon a legal matter when required. The prosecuting attorney may interrogate witnesses before the grand jury when the grand jury or the prosecuting attorney finds it necessary, but no person other than the grand jurors shall be permitted to remain in the room with the jurors while the jurors are expressing their views or giving their votes on a matter before them. In all matters or cases which the attorney general is required to investigate or prosecute by the governor or general assembly, or which a special prosecutor is required by section 177.03 of the Revised Code to investigate and prosecute, the attorney general or the special prosecutor, respectively, shall have and exercise any or all rights, privileges, and powers of prosecuting attorneys, and any assistant or special counsel designated by the attorney general or special prosecutor for that purpose, has the same authority. Proceedings in relation to such matters or cases are under the exclusive supervision and control of the attorney general or the special prosecutor.
R.C. §2939.10