Ohio Rev. Code § 2108.40: Definition of death.

An individual is dead if the individual has sustained either irreversible cessation of circulatory and respiratory functions or irreversible cessation of all functions of the brain, including the brain stem, as determined in accordance with accepted medical standards. If the respiratory and circulatory functions of a person are being artificially sustained, under accepted medical standards a determination that death has occurred is made by a physician by observing and conducting a test to determine that the irreversible cessation of all functions of the brain has occurred.

A physician who makes a determination of death in accordance with this section and accepted medical standards is not liable for damages in any civil action or subject to prosecution in any criminal proceeding for the physician's acts or the acts of others based on that determination.

Any person who acts in good faith in reliance on a determination of death made by a physician in accordance with this section and accepted medical standards is not liable for damages in any civil action or subject to prosecution in any criminal proceeding for the person's actions.