Above and below are the photos of three killers. Do you notice any common traits? I would call your attention to their eyes and their mouths. They are difficult pictures for most people to look at, but there are important similarities to note. In all three their eyes don't match their mouths. While there are certain disease states that may cause the eyes to be opened wider than "normal", none of these three fit such a pattern. Eyes that are opened wider than normal for a brief moment are consistent with surprise - but surprise is the most fleeting of all emotions, lasting only for a second or two and in its full manifest, is accompanied by a wide open and rounded mouth. If surprise lasts longer than that, it has a component of insincerity.
Another emotion which has a facial expression of widely opened eyes - is fear. The face of fear however, has a mouth pulled out to the side with tightly stretched lips and a view of the teeth - usually the bottom teeth are more visible. The neck muscles are often prominently tightened and the head is usually retracted away from the object of fear. The nostrils are prominently flared as well. None of these photos are consistent with fear.
Rage, an extreme state of anger often accompanied by violence, shares the facial characteristic of eyes which are "white and wide" as well. This level of anger has a squared-off and open mouth with an accompanied baring of teeth and again - nostril flaring. None of the photos below demonstrate rage.
What these photos have in common is that in each case their eyes don't match their mouths - at least for any healthy or commonly seen emotion. All their mouths demonstrate smiles, while their eyes, being wider opened than normal - are consistent with an increased adrenaline state. These two findings don't match and are (fortunately) relatively rarely seen together. Whenever the body language of different parts of the face and body aren't congruent - a red flag should go up. Beware!
The top picture is Marshall Applewhite, and although he is not a murderer in the classic sense, he was the "Heaven's Gate" cult leader, who in 1997 led 39 others in a mass suicide.
The second picture (immediately below) is Jared Loughner, who was the shooter in the recent tragedy in Tucson, Arizona.
The last picture is Joseph Duncan, a convicted serial killer of at least seven people between 1996-2005.