Sex is the primary motive of lust killers, whether or not the victims are dead, and fantasy plays a large role in their killings. Their sexual gratification depends on the amount of torture and mutilation they perform on their victims. The sexual serial murderer has a psychological need to have absolute control, dominance, and power over their victims, and the infliction of torture, pain, and ultimately death is used in an attempt to fulfill their need. They usually use weapons that require close contact with the victims, such as knives or hands. As lust killers continue with their murders, the time between killings decreases or the required level of stimulation increases, sometimes both.