Kevin-
About 5 years ago I had a case that presented an interesting conflict of law issue between Connecticut law and Ohio law. The issue involved which state's law regarding the marital communications privilege applied to the facts of a Connecticut civil case arising from a multiple motor vehicle accident involving a fatality. After the accident, which occurred in Connecticut, my client had a conversation with his fiancee over lunch, which also occurred in Connecticut. My client discussed the accident with his fiancee, who then drove to Ohio. They were both later married in Ohio and resided there as a married couple as of the time the issue arose in the case.
When the other side attempted to depose my client's wife, who was living in Ohio, about the conversation she had with my client after the accident in Connecticut, I immediately filed a motion for protective order asserting both the Ohio and Connecticut marital communication privileges, as it was not clear to me which one applied (note that under Connecticut law the party spouse has standing to assert the privilege as to the deposition of the non-party spouse). My research revealed that the marital communications privilege in Ohio is statutory, whereas in Connecticut it is rooted in the common law. In both states the privilege may be asserted to prevent one spouse from being compelled to testify against another spouse in a civil proceeding. The policy behind these laws is that allowing one spouse to be compelled to testify against another would tend to undermine the harmony of the marital relationship, in which things are said in confidence as they are to one's own attorney.
What is really odd about the Ohio marital communications privilege is that by statute it extends to all communications AFTER the marriage is consummated and even after the marriage ends in a divorce, but not BEFORE the marriage when a couple is engaged, as was the case here. The Connecticut marital communications privilege does not have the same precise limitation, but the cases can be read as applying only to legally married persons and not common law spouses or fiancees.
The other side argued the privileges did not apply because they were not married when they had the conversation after the accident. I argued that the intent of the Ohio and Connecticut marital communications privileges is to preserve the sanctity of the marriage and that purpose would be defeated if it was not applied to a couple who, although only engaged, in fact did later get married (within a month after the conversation happened, if I recall correctly) and remained married as of the time that this motion was argued.
I won that argument, the motion for protective order was granted, my client's wife was never deposed (which was a huge victory for the defense), and I made some law here in Connecticut. In its decision, the Court never said whether it was applying the Connecticut or Ohio privilege, but it didn't matter because I had argued both states' privileges should produce the same result. I don't know if this issue has ever been litigated in Ohio with respect to an engaged couple, but I would be interested to know.
You should get yourself elected to the Ohio legislature and then amend that statute to include premarital communications between people who later do get married and are married when the issue arises. Otherwise that Ohio statute does not make any sense in these situations.