In my research with bullying/peer victimization, I have found the most violent and impulsive bullies tend to show little empathy for others.

And while I agree it is problematic to try and create a systematic way of "predicting" serial murderers, and as a researcher I want empirical research with repeatable or at least close to exhaustive numbers as possible to strengthen a view on predicting homicidal behavior, predicting the behavior of ANY human lends itself to problems.

Long interjection however, my point is, I would imagine being able to take someones life demonstrates a lack of empathy. So the part of the triad that speaks to animal cruelty (clearly a lack of empathy) and fire setting (again, not understanding the effect ones behavior has on others) seem plausible. I know "plausible" isnt what you were going for here Dr Ramsland but I think it is the best one can do when "predicting" human behavior.

I would love to see research with serial killers (or even violent offenders for that matter) that focuses on 3 different aspects of personality/experience: development of empathy, maternal influence (if any at all which I think tends to be a key factor), and finally, genetics.

I have read about the "Killer" gene-please dont press me for the source, i cant remember where it is from at this writing-that can be triggered (like some addictions) by a life experience.

I think in my proposed triad, lack of empathy is the key environmental factor in the development of a violent individual. But even the other two are related: an absent mother and a genetic predisposition to impulsive behavior with at least one single life experience (like being abused or abusing an animal) can combine to create the "perfect storm" introduced by a previous writer.

Just some thoughts after having read your article and reflecting on my own experience with the triad - I too had heard the attempts to predict (or explain) homicidal behavior based on these three behaviors. But I think lack of empathy can be noticed early and can lead to more questions and could head off a possible violent future.