A friend of mine interviews people for a living. One of her jobs is to figure out when someone’s being dishonest with her. When someone says he’s an electrician, she has a few questions she asks to see if he’s actually an electrician or if he simply knows how to wire in a new outlet.
All kinds of people call themselves Christians. My uncle once told me that every “Christian” businessman he ever met screwed him over. I assured him that those people weren’t Christians.
Unfortunately, you can’t ask a few questions and find out whether someone is really a Christian. For one thing, a person can have all of the right answers and still not be a Christian. We’re told that they’ll know we are Christians by our love. It’s that simple.
Now, no one’s perfect, and only God knows someone’s heart. However, if someone is behaving in selfish, illegal, immoral ways on a regular basis, chances are good that they aren’t really a Christian.