By definition, a serial killer is an individual who murders two or more people in separate events, driven by psychological reasons rather than money or war. Though relatively rare in comparison to the general population, there have been many serial killers of varying significance throughout the course of history. Due to the often psychopathic nature of a serial killer, it can be extremely difficult for authorities to accurate judge just how many victims the individual murdered. In most murder cases, the offender is likely to deny the charges, or understate the extent of their crime. When it comes to serial killers, it's often the case that the killer will claim more victims than they actually murdered, wearing the number as a badge of pride. This list takes a look at the 10 deadliest serial killers from history, who were successfully identified and convicted for their crimes using modern policing methods. As it's looking at psychologically-driven killers, war criminals such as Pol Pot or Adolf Hitler do not fall in the same category. Please note that many of these entries contain content that some readers may find disturbing.