Prof. Buss was on CNN as a quick interview pertaining to the BTK killer. He has a book out on serial killers. The part about twins I strained to hear from another room so I could have misinterpolated that part. maybe a CNN search has the transcript. I would interested as to what was said of twins.

I have never known an evil twin.

I do have 2 neighbors who I could imagine as psychopaths. One is a very charming biker who is always in full biker regalia. Extremely intelligent and capable of being very funny or very scary. But he has a full range of emotions so scratch that one.

The other is an accountant who shows absolutely no emotion at all. A cold fish to the extreme and owns a cache of guns that no one person could possibly carry.