Their ability to remain at large indicates that they do have control over their actions. The fact that the majority of them pick vulnerable victims is also another indicator that they are in control. Women and children are the most common victims of serial killers. However, to say that serial killers are completely normal would also be inaccurate. Charles Manson was made to go to school in a girl's dress, as was Henry Lee Lucas.
Many experts feel that each killing is a re-enactment of a traumatic childhood experience.
Each time Lucas killed, he was killing his mother. Many serial killers have had some kind of head injury in their past. This may somehow affect them, and is likely a factor in the killings. Others maintain that it is a genetic predisposition to kill. Some have had physical deformities.