Ohio Rev. Code § 2935.07: Person arrested without warrant shall be informed of cause of arrest.

When an arrest is made without a warrant by an officer, he shall inform the person arrested of such officer's authority to make the arrest and the cause of the arrest.

When an arrest is made by a private person, he shall, before making the arrest, inform the person to be arrested of the intention to arrest him and the cause of the arrest.

When a person is engaged in the commission of a criminal offense, it is not necessary to inform him of the cause of his arrest.