On July 13, 1966, Chicago was unfortunate enough to be holding Richard Speck, a merchant seaman on his way to New Orleans. Speck entered the home of nine student nurses, and killed all but one of them (possibly leaving her alive by mistake).
Though not technically a serial killer, but rather a mass murderer, he is included here because Speck became the subject of a new theory on violence. When he was found to have the chromosomal abnormality of being XYY, some scientists began to believe that this may give a person a genetic susceptibility towards aggression. Early assumptions about the syndrome included that it made men more aggressive and antisocial, gave them below-average intelligence, and even made them more prone to homosexuality.
It is now believed that though there are a disproportionate number of men in prison with XYY Syndrome compared to the normal population, the numbers still are not high enough to indicate that the syndrome is linked directly with violence.
Accepted symptoms now include increased height, a tendency towards delayed maturation, being more physically active, being prone to learning disabilities, and a tendency to be more impulsive.
However, it is now reported that Richard Speck was misdiagnosed, and was not XYY at all.
(Reader may find it interesting to note that John Wayne Gacy was XYY, and that a slightly larger population of XYY men are found in prison than in the general population),
Post Traumatic Stress Syndrome, or "Shell Shock"
Many killers have exposure to post traumatic stress syndrome, otherwise known as "shell-shock". Shell-shock was first discovered by British doctors in 1914, and was originally thought to be caused by bursting shells creating a vacuum that disturbed the cerebro-spinal fluid, and upset the brain. From 1914 to 1918, the doctors observed 80,000 men, or approximately 2% of the soldiers exposed to active service, displaying symptoms of shell-shock, which early on, include tiredness, irritability, giddiness, lack of concentration, and headaches.
The current diagnostic criteria for post traumatic stress syndrome include the patient experiencing intense fear, helplessness, or horror over witnessing or being engaged in extreme violence or a threat of violence, disturbing recollections of the event, distressing, recurrent dreams, flashbacks, or feeling like the event is happening all over again, and distress when exposed to physical or psychological cues that symbolize the event.
Many people affected by the disorder have problems with social avoidance, detachment, an inability to have loving feelings for people, diminished interest in activities, outbursts of anger, and exaggerated responses.
A young child exposed to a parent with this syndrome could easily be affected by their parent's psychological problems. Abuse on the parent's part could also give the child post traumatic stress syndrome themselves. As you will read, some of the outlined killers were exposed to graphic violence or abuse.
Several of the killers on this page, it should be noted, have been exposed to, and influenced by, people in their life who worked in law enforcement, or served in the army during wartime, and may or may not have been suffering from post traumatic stress syndrome.