Close examination of serial killers reveals many similarities in their lives, personalities, and attributes. To what extent is their predilection to violence genetic, and to what extent influenced by their circumstances? In other words: nature or nurture?
A checklist to identify a potential serial killer might include: suffering abuse from a parent; an alcoholic parent; an underprivileged childhood; witnessing abuse of or by a parent. However none of these things, or even all of them combined, inevitably create a serial killer.
It is generally accepted that a susceptibility to alcoholism is genetic. However alcoholism itself is not. Same with violent tendencies. If a parent is abusive, it is likely the child will grow up with violent tendencies. But why? Because of genetic programming, or because abuse becomes normality to them through experience?
Either way, it is a very large jump from abuse to killing somebody. What causes somebody make that jump?
There is a disease called Munchausen's Syndrome, and Munchausen's Syndrome by Proxy. The syndrome starts when somebody seeks attention and sympathy by faking or exaggerating symptoms of an illness. It sometimes, but not always, moves on to the "Proxy" stage: when somebody causes illness or injury to a third party (usually a child in their care). Sometimes they "save" their victim, bringing praise upon themselves. Sometimes the victim dies, resulting in sympathy and more attention for the perpetrator. Beverley Allitt is a prime example of this type of killer: she started by wearing false casts on her arm and complaining of back pains, then moved on to cutting herself with broken glass, and finally ended up as a nurse killing her child patients.
My take on this syndrome, particularly in Allitt's case, is a lack of attention. Allitt was one of four children, and was an overweight adolescent. Under certain circumstances, getting attention in any way possible can become a driving force. But don't take this to mean that I'm blaming her parents, society, or anybody other than herself. There was obviously something very broken inside her that caused her to take the conditions dished out to her and warp them into a drive to kill children.
A disease such as that is only one explanation for why somebody kills. Many serial killers are acting out bizaare fantasies or trying to kill an aspect of themselves or somebody they think has wronged them. Men who kill prostitutes may be impotent. Men who kill blonde women may have been scorned by a blonde woman in early adolescence. Men who kill gay men may be repressing their own homosexual urges. Who knows?
That's what makes the whole area such a fascinating study. Nobody knows!