There's a woman on youtube and the internet who claims you can understand a person's character from their physical characteristics. For instance, if you can see the whites of their eyes underneath their irises when you are standing level with them, they are likely to be very psychologically disturbed. According to her, 20% of serial killers have this attribute.
This seems dangerous and appealing at the same time. Does anyone know if there is any scientific evidence to back this up?