Even the most highly-trained psychologists and police officers are incapable of predicting who has it in them to become a serial killer, but there are some common traits that the most prolific killers in the world share.
Thankfully, people who are mentally imbalanced enough to murder others make a minuscule percentage of the population, so many people will display these signs without going on to kill. Although it's highly unlikely you will cross paths with a serial murderer, it still pays to be informed...
1. Childhood Abuse and Neglect
A staggeringly large proportion of serial killers have survived extremely traumatic childhoods riddled with physical, verbal and sexual abuse. The FBI conducted a study which interviewed dozens of serial killers, and with every individual they found “similar patterns of severe childhood neglect.”
This is dangerous because there are stages in a child's development that are crucial to learning about love, empathy and appropriate ways to interact with those around you. Sometimes, when these traits are not imprinted on the child, it may not be possible for them to be learned later in life.
Chilling example: Aileen Wuornos (a prostitute who murdered six clients) was abandoned by her mother just before her fourth birthday and raised by her maternal grandparents.
Unfortunately, this living arrangement was the beginning of years of abuse and the young Aileen was sexually abused by her grandfather and raped by his friends.
She became pregnant aged fourteen from these attacks and was forced to give her baby away for adoption after giving birth in a home for unwed mothers.
After her grandmother died when she was 15, Aileen was thrown out by her grandfather and began working as a roadside prostitute to survive.
2. Poor School Reports and Employment Records, Despite Intelligence
Serial killers are generally of above average intelligence, largely because of the complicated logistics of killing more than one person and getting away with it...at least temporarily.
A #serialkiller's inability to integrate with others and their lack of respect for social norms means that are unlikely to be able to progress in their careers or remain employed for more than a few months at a time.
Chilling Example: Ted Bundy (who murdered at least 30 people) was reported to have an IQ of 136, but this wasn't enough to enable him to excel in his studies. Bundy dropped out of two universities to work a string low-paid menial jobs and made his main ambition in life kidnapping and murdering women.
3. Excessive Antisocial Behavior
Somebody who has antisocial personality disorder is ultimately a person with no sense of guilt or remorse. These people also tend to display high rates of aggression, compulsive lying, and an inability to take responsibility for their actions .
Chilling Example: John Wayne Gacy, who raped and murdered 33 teenage boys and men, had no remorse for his crimes whatsoever. Instead, he called his victims "worthless little queers and punks."
4. Obsessive Fantasizing
Haunted by violent and twisted desires that they are forbidden to make a reality, potential serial killers will obsessively and feverishly imagine the depraved fantasies they wish to act on.
This fantasizing is often accompanied by compulsive masturbation, particularly as serial killers in the making often find it hard to form relationships with actual human partners.
Chilling example: 'Rostov Ripper' Andrei Chikatilo actually masturbated so frequently and violently that he developed "dreadful scarring" on his penis.
5. Head Injuries
It might be a common turn of phrase to joke that people must have been dropped on the head as a child, but head injures are serious business.
Over half of serial killers have suffered a violent head injury. In particular, damage to the pre-frontal cortex - the area of the brain used for judgement and planning - is particularly dangerous when it comes to increasing aggression.
Chilling Example: Richard Ramirez, also known as the Night Stalker, sustained two serious injuries when he was a child. When he was just two years old a dresser fell on top of him, causing a gaping laceration requiring thirty stitches. When Ramirez was five years old he was knocked unconscious by a swing at a local park. Both of these injuries could have potentially damaged his frontal lobes.
Voyeurism often appeals to serial killers, both as a way of enjoying sexual pleasure without needing a close or emotional relationship with another person and as a way to violate another person's privacy. A substantial number of killers begin with pettier sexual crimes before developing to assault and murder to quell their passions.
Chilling Example: Danny Rolling was caught spying on cheerleaders dressing and bathing and it was common knowledge among his peer group that he was a peeping Tom. Rollin went on to commit eight sexually motivated murders of local students.
The MacDonald Triad
Named for the scientist who made the connection, the MacDonald Triad is three characteristics, which all indicate the possible development of a serial killer.
Of course, the majority of children wet the bed until they around five years old, but persistent bed-wetting into teenage years and beyond can be an indicator of the neuroses, trauma and psychological unrest that is typically found in people who go on to kill.
Chilling Example: Alton Coleman, a spree killer who murdered seven people, was a persistent bedwetter. So much so that he was nicknamed "pissy" by his peers.
Pyromania is common in future serial killers - it makes sense for a twisted mind to find these acts of uncontrollable destruction fascinating.
Chilling Example: Before Ottis Toole went on to murder at least six people, he was a serial arsonist who was sexually aroused by the destructive power of fire.
9. Animal Torture
Their typical lack of empathy and inability to experiment on the actual targets of their twisted desires often compels serial killers to torture and kill animals during childhood and teenage years.
Chilling example: Many serial killers kill animals before moving on to humans, but Jeffrey Dahmer is a famous case: he impaled a dog's head on a stick and left it out for people to see.