My husband's ex had a pretty bad psych eval and she still ended up retaining primary custody and being able to move my step daughter 3,000 miles away.
The court house is the only place you will ever see pigs fly. It is a subjective decision that is made about a family that is in crisis. Most often both parents are far from their best behavior at that point. I think in most cases the judges beleive neither is that much worse or better than the other.
