Perhaps the single most critical stumbling block that currently stands in the way of understanding serial murder is the disagreement among researchers and law enforcement personnel about .

how to define the phenomenon

Explanation: The disagreement between the Federal Bureau of Investigation (FBI) and Researchers stems from the definition of serial murder.

While the Federal Bureau of Investigation explains serial murder as a series of two or more events carried out at different location and usually perpetrated by one person.

Researchers explain serial murder to mean a series a three or more killings perpetrated by one person in separate events with a break between each killing event in other to mark a distinction between serial murder and spree murder.

However, the break between each cooling usually called cooling period isn't recognized by the FBI.