Legal Question in Landlord & Tenant Law in California

You can't present evidence in a demurrer. A demurrer is a motion that assumes the allegations of the complaint are true and then argues that under the law even if they are there is no right to relief. The court can, however, take judicial notice of public records in deciding a demurrer, so it is possible to try to get the court to take notice of a certified copy of your deed. To do that, however, is somewhat technical. So you probably should get an attorney to help you with that.

As for whether it would clear the matter up, without seeing exactly what he filed, it would be impossible to say.

If he were the room renter, I don't see how he could file an unlawful detainer against you -- unless I have it backwards. The landlord is the one who files the unlawful detainer. This includes the tenant who sublets to another.