I don't think you can. They could be quite, withdrawn, angry, overly sexual, aggressive, violent, or depresses, and live in a fairly functional family. Everyone deals with trama, regret, greif, and anger differently. You would have to get to know the person and chat with them alot, and pay attention to the other family mber behavior. Even then you can't know for sure.
The question might be better answered if you ask, "How can you tell if someone comes from a normal family?" Seriously, I don't know anyone anymore whose family isn't dysfunctional on some level. (I'd add an "lol" but it's so hard to laugh about sometimes.)