Before you even start building a profile it is important to define what type of offender you will have to deal with as it will determine what approach to the crime you will have to use. This classification is important as you will not build the same profile if you have to work on a mass murder, a single homicide, or a series.
- If there is one single victim, in a single event, in a single environment you have to work on a single homicide
- If there are two victims, in a single event, in a single environment you have it is a double homicide
- If there are three victims, in a single event, in a single environment you have it is a triple homicide
- If four or more victims are killed in a single event, in a single environment, you have to deal with a mass murderer: generally a white male who had to deal with such a high level of pressure in his life that he cannot cope with it anymore and snaps into a murderous rampage. He usually kills impulsively a group of people (can be specific group or totally random) with rare violence as he is completely lost control of his actions. This behavior often precedes his own suicide or a confrontation with law enforcement (suicide by cop). Be aware that this individual is very dangerous and will take down as many people as he can (victims, hostages, policemen)
- If two or more homicides are committed in a unique event but in two or more different places, the individual is called a spree killer. He is usually only half in control of his actions. He could be to certain lengths compared to a mobile mass murderer, but with a lesser tendency to commit suicide.
- If three (or two depending on the definition) are perpetrated during three (or two) separate events and in three (or two) different locations, you will have to deal with a serial killer. The way to really make the difference with the last two types is that usually serial killers have a cooling off period (a period of time where they don't kill).
But these typologies are not fixed at all, and you have to be very careful not to be too strict about them. As an example, we can take the case of a single homicide: it is not because you work on a single homicide that you are not facing a serial killer. Indeed, there might be elements on the crime scene (ritualization of the scene, high level of ante-mortem mutilation, dominance of sexual activity on the scene... the major element to determine on a single homicide scene is if the murderer enjoyed or showed signs of pride in his acts) might indicate that the individual who committed the crime might do it again in the future. It is now a fact for the FBI that a murderer does not necessarily need to have killed three times to be labelled a serial killer.
Also, a murderer can be classified in several categories, either in a single event, or from one crime to the other. The best example is Ted Bundy who was a classical serial killer throughout his life until he got caught. Being in prison and escaping triggered something in him that made him become a mass murderer when attacking a sorority while on the run.