Bait and Switch: The Cannibal Crimes of Joachim Kroll
While Kroll was apparently none too bright, he was not so delusional as to be considered insane at the time of his murders. Nor did he show shame or remorse over what he had done to his victims, which places him in the category of psychopathy, with the addition of being sexually sadistic. A great deal of work is currently underway regarding the nuances of psychopathic manifestations, with the notion that there's more to it than earlier psychological models have revealed.
In The Psychopath: Emotion and the Brain, Blair, Mitchell and Blair address the problems with neurocognitive systems that appear to be involved in the type of emotional learning implicated in repetitive aggression. They propose that something has gone wrong, developmentally, with the brain's ability to learn emotional responses to the world (which supports the evidence that psychopaths fail to learn from consequences). If an individual's neurocognitive system has been impaired at an early age, they state, he or she "will present with the emotional difficulties associated with psychopathy." Because these impairments interfere with the processing of appropriate socialization, such people are at risk for elevated levels of the type of aggression that serves their needs.
Nevertheless, psychopathy is not an explanation for behavior like Kroll's; it's only a frame. Martingale indicates that Kroll blamed his deviance on an experience he'd had during puberty, when he was sexually aroused upon witnessing the slaughter of pigs. Since he was not educated or clever enough to devise an explanation to please the forensic psychiatrists, an experience that linked his sex drive with blood, butchery, and death could be at least an influence on his aberrant behavior.
Something is certainly wrong when people become compulsive murderers, especially with such added behaviors as blood-drinking, dismembering, necrophilia, and cannibalism. Schlesinger takes up the notion of compulsive killing in Sexual Homicide. He makes a distinction between impulsive serial killers, who are generally disorganized and without a clear pattern to their homicides, and compulsive killers, who act from an intense drive and have a plan and a sense of purpose. Compulsive murders, he indicates, "are determined entirely by internal psychogenic sources, with little environmental influence. The urge to commit the act is powerful, and the offender may experience inner discomfort and anxiety if he attempts to resist action." Because compulsion is similar to addiction, compulsive killers tend to repeat their crimes, maintaining a similar method. In part this is because the fusion of sexuality and aggression have eroticized the violence. Since the male sex drive tends to be stronger than that of females, this is a pattern of crime almost exclusive to males.
In addition, Schlesinger adds, "compulsive offenders have a disturbance in the sexual instinct that results in aberrant sexual fantasies in which gratification is achieved through various forms of aggression. His satisfaction cannot be achieved with murder alone; it also requires some enactment of their fantasy." Generally, compulsive murder becomes a matter of dominating victims to feel in control.
Nevertheless, fantasy itself is not a sufficient explanation. Many people have violent fantasies without acting on them. What's missing in such people, Schlesinger explains, is "a corresponding state of tension." Acting out frees compulsive killers from this pressure. They can exercise restraint if necessary, but they prefer the gratification, so they will plan a crime as well as act on opportunity. However, given the low incidence of compulsive killers around the world, compared to other types of murders, it seems that many things must go awry in a number of areas (biological, psychological, environmental) before the conditions will generate this type of dangerous offender.