The issue of nature in the formation of the serial killer arises (in concert with the environmental component) from one fact: Over 99.9% of serial killers, around the world, in all cultures and socioeconomic groups, are male.

If we look at the XY chromosome, which is male defining, then we logically assume that there is some change, or mutation, in that chromosome grouping that, in concert with the pubertal hormonal and brain changes, predisposes one to become a serial killer. As of now, we have no definitive test to demonstrate this probable change. We do know that serial killers are not behaviourally unusual until that time of their development, and any attempts we make to study them (by implanting electrodes in their brains, or other neuro-chemical tests), are not permitted to be done by current law.

Perhaps in the future, laws will allow this testing. Also, nature/nurture has been so much debated in the literature that it appears we still need to maintain this unfortunate dichotomy. But, we all know that a simplistic separation cannot ever be successful. Because we are human, perhaps we need definitive proof - not yet possible on either side of the debate. Thank you.