This question is flawed. There is no such thing as a good nor evil person; only a person who has done good things or bad things. But just because someone has done something bad doesn't mean they're going to continue doing many bad things. It doesn't make them a bad person - the same goes for vice versa.

Q: "Can you look into the eyes of a person and tell if they have a propensity towards doing bad/good things?"
A: Probably not. Most people that think they can base that judgement off of extraneous but not unrelated details. They stereotype their subject of interest based on many things: apparent social class, skin color, tattoos, piercings, etc