No Appparent Motive.

A serial killer is the most mysterious and devious of criminals because he has no apparent motive for committing his crimes.

With an inner urge to assault, sexually abuse, and kill, nurtured by endless fantasizing.

A few serial rapists and killers have video- recorded their crimes; the videos show them to be exquisitely aroused by their victs cries of pain, and callous to their pleas for mercy. To normal human being, the tormentors appear to be monsters in human guise.

Def.

"a series of two or more murders, committed as separate events, usually, but not always, by one offender acting alone".