Actually, a good way to learn a great deal of valuable information about a prospective partner whose background is unknown to you is to hire a service to perform a background check. Again, I know that sounds cold and clinical, but safety first should be the cardinal rule in this day and age. I worked as a paralegal for almost eight years for a team of prosecutors on domestic violence crimes (ranging from simple assaults and protective order violations to stalking and near-homicides, from simple property damage to outright burglaries, etc.); that experience forever changed my viewpoint about social relations. (It should be noted that I did nothing from my list when I started dating the man who became my DH over 14 years ago.)
At the minimum, take a trip to your local courthouse and learn how to do a simple civil and criminal history check in your jurisdiction. And if there are any - and I mean ANY - criminal charges involving domestic violence, or civil domestic restraining or protective orders, run like hell.
A-Jock