Killers both fascinate and terrify us. When a sudden outbreak of deadly violence shocks a community or the world, it's only reasonable to wonder if it could have been predicted -- if there were any warning signs that could identify murderers before they take a life. Unfortunately, there are so many motives for killing, ranging from money to passion to mental illness, that identifying a potential murderer is very difficult. Nonetheless, there are a few warning signs that can apply to some of the most common types of killer.
A History of Violence
Some killers don't show a tendency to harm others until they kill, but in many cases murder is part of a long-term pattern of violence. Types of violence that can escalate to killing include domestic violence. A 2011 Independent Police Complaints Commission report identified multiple cases of murder in which victims had previously made domestic violence claims against their killers. Similarly, a history of lesser crimes, such as assault or robbery, could signal violent, aggressive tendencies that may lead to an individual going on to kill.
Some mental health conditions, such as schizophrenia, can lead to violence if not treated. Similarly, substance abusers who are not receiving the care they need can run the risk of becoming violent. This connection can be overstated; mental health campaigners worry that calling murderers "crazy" can stigmatise these illnesses, preventing sufferers from seeking treatment. The vast majority of individuals with mental health issues are non-violent, but all benefit from early diagnosis and receiving medical attention.
A 2004 study of homicides in Paris during the 1990s identified some common traits among killers. The study found they were often people with limited economic opportunities, struggling with financial or family problems and cut off from sources of support. In these conditions, the study's authors contended, a sense of desperation led to indifference to the consequences of their actions. In other words, these killers felt that they had nothing to lose.
Lack of Empathy
There are many different types of murderers, ranging from spree killers to those who nurse a grudge against a particular individual. One thing many murderers share, however, is a lack of empathy -- an inability to understand the feelings of others or consider their well-being valuable. In some cases, this may be a symptom of sociopathy, a condition which renders an individual unable to identify with others or feel remorse for their actions. Such individuals are remorseless, deceitful and capable of remarkable cruelty.