There are seven types of motives that drive serial killers to kill. These include visions that the killer claims have come to them “guiding them to kill”, a desire to rid the population of a certain race or type of individual, hedonistic reasons; meaning the killer gets pleasure from the violence, lust; in which they kill for sexual gratification (whether the actual act of sex occurs or not), for thrill, for personal gain such as money or material goods, and power seekers, who like to control the death time of others in order to feel in control of their own lives.
Serial killers usually spread out their killings and are typically repeat offenders because the actually act they committed did not live up to their expectations. The killings tend to gain in severity as the killer becomes more experienced and are not stopped until they are jailed, or die themselves. Arrested serial killers who have received counseling and therapy have shown no improvements in their mental condition after treatment and these rehabilitation practices have even worsened the problem.
Scientists now believe that in the future there might be a cure for the defect in the brain on the medulla oblongata which is responsible for emotional reaction. While the technology, availability and ethical concerns are limiting this possibility right now, the theory is out there being worked on.