Ohio Revised Code Title XXIX. Crimes Procedure § 2939.031

When it appears to the judge impaneling a grand jury that the inquiry is likely to be protracted, or upon direction of the judge, an additional or alternate juror shall be selected in the same manner as the regular jurors in the inquiry are selected. The additional or alternate juror shall be sworn and seated near the jury, with equal opportunity for seeing and hearing the proceedings, shall attend the inquiry at all times and shall obey all orders and admonitions of the court or foreman. When the jurors are ordered kept together, the alternate juror shall be kept with them. The additional or alternate juror shall be liable as a regular juror for failure to attend the inquiry or to obey any order or admonition of the court or foreman. He shall receive the same compensation as other jurors, and except as provided in this section shall be discharged upon the final submission of the bill to the foreman.

If before the final submission of the bill to the jury, a juror dies or is discharged by the judge or foreman due to incapacity, absence, or disqualification of such juror, the additional or alternate juror, upon order of the judge or foreman, shall become one of the jury and serve in all respects as though selected as an original juror during the absence or incapacity of an original juror.