Psychology is a behavioral science that is sometimes referred to as a “soft” science. If you think about mathematics and the sub-discipline of trigonometry (the study of angles), a shape such as a triangle has to have all of its angles add up to 180 degrees, and a square 360 degrees etc. If a shape’s angles don’t add up to 180 degrees, it can’t be – and there’s no way it can be – a triangle. The “rules” are firm and rigid on this. There is also a “predictive” element to this, in that once you know a shape angles add up to 180 degrees, you will also know that it has three sides etc. However, when you look at how the DSM defines certain personality orders, you can diagnose two different people with a particular disorder, without them sharing many or any of the same diagnostic criteria e.g., for someone to be diagnosed/classified as having Borderline Personality Disorder they must exhibit five out of a possible nine behaviors, meaning that two people diagnosed with BPD, may potentially only share one particular criteria/behavior. Also, in these lists of behaviors/criteria, each one is weighted the same. Obviously, the person making the diagnosis is able to add their experience and expertise to the process, but this makes the method “less” scientific, as a somewhat subjective and less predictable element is now involved. This means that diagnosing someone with a personality disorder such as narcissism is not a “neat” process, and that different individuals can exhibit the disorder in different ways; this is why there is the need for subtypes and variants of disorders. This, however, leads to its own issues e.g., if we need so many different sub-classifications of a personality disorder, how valuable/important is a diagnosis? This means it is often more productive to look at particular behaviors associated with a personality disorder and identify which ones are “troublesome” rather than simply look to classify someone as this or that. However, in forensic settings this can be an issue e.g., the prosecution may want to convince the jury that the defendant is a psychopath, with the defense arguing that the individual in question doesn’t actually meet the necessary criteria for such a diagnosis etc. One of the cases that highlights this issue is that of Dennis Nilsen.
Dennis Nilsen readily admitted to the police that he killed fifteen men in a five-year period (1978-1983), after a Dyno-Rod employee found human bone fragments in Nilsen’s drain; there is evidence to support the fact that Nilsen wanted to get caught, as he’d told his landlord that unless the drains of his flat/apartment weren’t unblocked he wouldn’t pay his rent – knowing full well the reason why they were blocked. Nilsen targeted homeless individuals and those on the fringes of society. Whilst all of those he killed were men, and Nilsen was a homosexual, there is nothing about the killings to suggest that they were sexual in the way we might think about a sex-crime such as rape. After he killed his victims, usually by strangulation, he would clean them, and then “enjoy” their company such as watching TV with them, and “admiring” their naked bodies and the control he had over his possessions. It is clear that Nilsen had mental health issues however he didn’t neatly conform to any mental illness or personality disorder, something which is true of many active shooters and killers i.e., someone who goes on a killing spree is clearly not in a healthy state of mind but in many instances an identifiable mental illness or even personality disorder isn’t present. The defense in the Nilsen case largely rested on the idea that Nilsen had acted due to diminished responsibility caused by his mental state; whilst he acknowledged that he had killed the people whose deaths he was being tried for he wasn’t fully responsible for his actions – this would mean that he was guilty of manslaughter not murder, meaning that the judge would be limited in the length of the sentence he was given (theoretically he could have been out in fifteen years). Two different psychiatrists made the argument that Nilsen had both traits of narcissistic, schizoid and borderline personality disorder and that this constituted an “unspecified personality disorder” (something recognized in DSM-V), that provoked/caused him to kill.
One of the issues that the defense had in their “diminished responsibility” argument was that Nilsen couldn’t be cleanly or neatly classified as having a single and distinguishable personality disorder. A juror has an idea of what a psychopath or narcissist is, even if they may not fully understand the clinical definitions of these disorders or why they are diagnosed in the way that they are e.g., the term psychopath is often used colloquially to refer to someone who doesn’t care about others, and narcissist to describe someone who loves themselves etc., and whilst these can be characteristics of these disorders they fall a long way short of what would be needed to actually make a diagnosis of them. Nilsen didn’t fit neatly into a particular hole. It is likely that Nilsen’s murderous actions were driven by a sense of loneliness and emotional indifference (two traits of Schizoid Personality Disorder), a grandiose sense of self-worth and importance (features of Narcissistic Personality Disorder), and anger/frustration/violence at an ended relationship (something those with borderline personality disorder may exhibit), when a grandfather he was close to as a young child died i.e., he had characteristics and traits of many personality disorders which led – not inevitably – to him becoming a killer. However, because he couldn’t be easily/readily defined with an existing/identifiable personality disorder, the defense was unable to convince the jury that his actions were due to diminished responsibility as a result of his mental health.
We tend to use the terms narcissist and psychopath a little too freely, without fully understanding which of the traits concerning these personality disorders may manifest themselves negatively and potentially violently etc. I am not going to argue that a lack of empathy and remorse are positive or welcome character traits, however there may be times when these character traits may give someone an advantage that leads to something positive e.g., there may be times when “clinical” rather than “personal” thinking leads to the greater good. This means that when we are looking to predict aggression and violence, a diagnosis of a particular/individual personality disorder or mental illness may not actually help us in assessing risk, and we are better looking for the presence of certain character traits of various disorders that are likely to result in destructive behaviors.