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Serial Murder Versus Mass Murder

Two very different types of crime.

Mass Murderer Dylann Roof
Source: Public Domain: Mugshot

Mass murder is sometimes confused with serial murder by the news media and the public in general. Such confusion is not surprising. Up until 1974, criminal justice practitioners used the term mass murder to refer to both types of multiple homicide.

Today, however, criminologists, forensic psychologists, criminal justice professionals and legislators recognize that serial murder and mass murder are two very different types of crime with very different motivations and goals on the part of the perpetrator.

Let us start by examining serial murder. There has been considerable debate among experts over the years regarding the exact criteria and definition of serial murder. During the past 40 years, various definitions of serial murder have been used by law enforcement officials, clinicians, academicians, and researchers.

While these definitions normally share common elements, they differ on specific requirements such as the number of murders required, the types of motivation and the temporal aspects of the murders.

Typically, definitions of serial murder specify a certain number of murders, varying from two to ten victims, as noted by the FBI in an influential 2005 report on serial murder. This quantitative requirement distinguishes a serial murder scenario from other categories of murder, especially single homicide, which is by far the most common act of murder in the U.S.

The classic definition of serial murder required a period of time elapse between the murders. This pause or break between killings was necessary to distinguish between a mass murder, which is a one-time event, and a serial murder, which has multiple incidents. The original definition of serial murder thus required a temporal separation between killing incidents described as a cooling off period or emotional cooling off period.

Perhaps due to the debate among professionals over the exact definition of serial murder, the U.S. government actually attempted to formalize it through legislation on one occasion. In 1998, a federal law was passed by the United States Congress, titled Protection of Children from Sexual Predator Act of 1998 (Title 18, United States Code, Chapter 51, Section 1111). This law includes the following definition of serial killings:

The term ‘serial killings’ means a series of three or more killings, not less than one of which was committed within the United States, having common characteristics such as to suggest the reasonable possibility that the crimes were committed by the same actor or actors.

This federal law provides a definition of serial murder but it is limited in its usefulness because it was only designed to establish criteria for when the FBI could assist local law enforcement agencies with their investigation of serial homicide cases.

At a major symposium on serial homicide in 2005, the FBI reduced the minimum number of victims from three to two in its definition of serial murder. The FBI did this for its own purposes and to satisfy its own institutional needs—that is, to afford itself greater flexibility and breadth in determining when and how to pursue potential serial murder cases. The FBI argued that the older criterion of three or more victims was arbitrary and unnecessary for investigative purposes.

In addition to lowering the minimum number of murder victims in 2005, the FBI also eliminated the cooling off period from its list of required serial homicide criteria. Similar to the rationale it used in lowering the number of victims, the FBI argued that the cooling off period is not a useful requirement for the purposes of criminal investigation.

It is important to note that the term serial killer is relatively new. As explained by Peter Vronsky in his 2004 book "Serial Killers: The Method and Madness of Monsters," the term was probably coined by the late FBI agent and profiler Robert Ressler, who said that he believed the term “stranger killings,” frequently used during the mid-twentieth century, was inaccurate because not all victims of serial killers are strangers.

Ressler was lecturing at the British police academy at Bramshill, England, in 1974, where he heard the description of some crimes as occurring in series, including rapes, arsons, burglaries, robberies, and murders. Ressler said that the description reminded him of the movie industry term “serial adventures,” which referred to short episodic films, featuring the likes of Batman and the Lone Ranger, shown in theaters on Saturday afternoons during the 1930s and 1940s. Each week, youthful matinee audiences were lured back for the next installment in the series by an inconclusive ending known as a “cliffhanger” that left them wanting more.

Ressler recalled from his youth that no episode had a satisfactory conclusion and the ending of each one increased rather than decreased the tension in the viewer. Similarly, Ressler believed that the conclusion of every murder increases the tension and desire of a serial killer to commit a more perfect murder in the future—one closer to their ideal fantasy. Rather than being satisfied when they murder, serial killers are instead agitated toward repeating their killings in an unending “serial” cycle.

Now, let us turn to mass murder. It is the act of murdering multiple people, typically simultaneously or over a relatively short period of time. Mass murder may be committed by either individuals or organizations. Mass murder may also be defined as the intentional and indiscriminate murder of a large number of people by government agents.

Examples of mass murder by government agents are the shooting of unarmed protestors, the carpet bombing of cities during wartime, and the random execution of prisoners or civilians. The largest mass killings in history have been attempts to exterminate entire groups or communities of people, often on the basis of ethnicity or religion. Some of these mass murders have been determined to be acts of genocide and others to be crimes against humanity by the United Nations Security Council or International Criminal Court (ICC), but often such crimes have led to few or no convictions of any type.

The focus of our discussion here, however, is on mass murder committed by an individual, or occasionally, by more than one individual. Mass murderers of this variety may fall into any one of a number of categories, including but not limited to, killers of family members, co-workers, students, or random strangers.

The FBI defines mass murder of this type as killing four or more persons with no cooling-off period between the murders. Stated differently, the FBI classifies mass murder as a single incident in which a perpetrator kills four or more people, excluding herself. The FBI specifically defined mass murder as a single event in order to distinguish it from serial murder.

In a mass murder committed by an individual, the victims may be either selected randomly or specifically targeted for a reason that only makes sense to the perpetrator.

The individual motives for mass murder vary greatly. A common motivation for mass murder is retaliation or revenge, but other motivations are possible, including grandiosity and the need for attention or fame. A mass murder sometimes occurs when the perpetrator, who may be deeply troubled, suffers a psychotic break from reality and strikes out at his perceived tormentors in a blitz-like attack.

Unlike serial killers, mass murderers are frequently, but not always, killed at the scene of the crime. Sometimes they are shot by law enforcement officers called to the crime scene, which is often referred to as “suicide by cop,” while other times mass murderers take their own lives in a final and deliberate act of suicide.

From a social-psychological perspective, mass murder is frequently an act of vengeance against society committed by a desperate and fatalistic individual who has no intention of going away quietly or returning to kill another day.

It is also important to note that serial murder is currently on the decline while mass murder, more specifically, mass public shootings, are on the rise.

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