Well, if you get caught speeding on a road, you can't use "I didn't know what the speed limit was" as a defense. If you are going to drive on the road, it's your duty to find out what the speed limit is.I don't know. I thought that intent, mens rea, or whatever you call it counts for something? That's why I'm asking. (eg. I have a friend who slept with his sister and got away with it... he didn't know she was his sister.)
So the final answer, that I can take as gospel is: it doesn't matter? Is this what you are saying?
If you're going to engage in a relationship with a co-worker, I think it would be your duty to find out what the status of your co-worker is.