Ohio Rev. Code Ann. § 135.39

A county treasurer, county deputy treasurer, or members of a board of county commissioners, when acting as investing authorities, and their bondsmen or sureties shall be relieved from any liability for the loss of any public moneys deposited or invested by them when they have acted pursuant to law or an ordinance or resolution adopted by a county pursuant to a charter adopted under Article X, Ohio Constitution, but in no event shall liability attach to a treasurer, deputy treasurer, or member of a board where the proximate cause of the loss is due to a risk arising from an investment reasonably made under their authority as investing authorities.