Psychopathy, schizophrenia, narcissism, persecutory delusions and paraphilias: what science says and what an investigator needs to know

In films the culprit is often "the madman": the brilliant psychopath, the violent schizophrenic, the monstrous necrophile. And facing him is the profiler who, looking at a crime scene, reconstructs his mind with almost magical precision.

The scientific literature tells a very different story. And anyone who, like me, works in investigations has a duty to know it, for two reasons: because wrong ideas lead to wrong conclusions, and because in day-to-day work you really do meet vulnerable people, both among those being investigated and among clients.

A note on method, and three important clarifications. I do not make diagnoses: a psychiatric diagnosis can only be made by a mental health professional after a direct assessment. I do not give advice on medical treatment: I report what the scientific literature says. In Switzerland, crimes are the responsibility of the police and the public prosecutor, not a private investigator. This article is for general information, not a tool for labelling people.

First of all: a mental disorder is not a crime

This is the starting point, and it must be said clearly.

• The vast majority of people with a mental disorder do not commit violent crimes.
• Most violent crimes are committed by people without a serious mental disorder.
• Many studies indicate that people with serious mental disorders are more often victims than perpetrators of violence.
• Alcohol and drug use is a far more significant risk factor for violence, in the general population as in people with a psychiatric condition.

The image of the "dangerous madman" is not only wrong: it fuels stigma, discourages people from seeking help and, in an investigation, can push you to look for the culprit in the wrong place.

The investigator's lesson. A psychiatric label is not a clue. Saying "it must have been someone mentally ill" does not narrow the field of suspects: it distorts it. Investigations are built on facts, documented behaviour and evidence, not on prejudice.

How mental disorders are classified

To speak precisely, you need common reference points. The two main classification systems are:

In Switzerland and Europe the ICD is the official reference for health statistics, while the DSM is widely used in research and clinical practice. The two classifications are similar but do not always coincide, and some everyday words, such as "psychopath" or "maniac", do not correspond to official diagnoses.

Psychopathy

What it is

Psychopathy is probably the most used, and abused, concept in criminology. The American psychiatrist Hervey Cleckley gave a classic description of it in 1941 in his book The Mask of Sanity. The Canadian psychologist Robert Hare later developed the best-known assessment tool today, the Psychopathy Checklist Revised (PCL-R).

In general terms, psychopathy describes a combination of:

What it is not

"Successful" psychopathy

Part of the research has looked at psychopathic traits in non-criminal settings, such as the corporate world. The book Snakes in Suits by Paul Babiak and Robert Hare (2006) popularised the idea of the "psychopath in a suit". It is an interesting line of research, but it must be handled with care: personality traits are distributed along a continuum, and not every ruthless manager is a psychopath.

The "Dark Triad"

In 2002 psychologists Delroy Paulhus and Kevin Williams proposed the concept of the Dark Triad: three socially aversive personality traits, distinct but correlated, namely narcissism, Machiavellianism and psychopathy. It is a research model of personality in the general population, not a diagnosis.

Schizophrenia

What it is

Schizophrenia is a serious psychotic disorder. According to the World Health Organization it affects about one person in three hundred worldwide. The main symptoms described by the classifications are:

The most common error

Schizophrenia does not mean "split personality". The term, coined in 1908 by the Swiss psychiatrist Eugen Bleuler, then director of the Burghölzli psychiatric clinic in Zurich, referred to a "splitting" of mental functions, not to two distinct personalities. So-called multiple personality corresponds to a different condition, dissociative identity disorder.

Schizophrenia and violence

Here the literature is clear and must be reported precisely. A review published in JAMA Psychiatry, pooling 24 studies covering more than 50,000 people with schizophrenia in 15 countries, found a modest but consistent increase in the risk of violence, and identified alcohol and drug misuse as a factor that roughly doubles that risk. As psychiatrist Seena Fazel of the University of Oxford stressed when presenting the results, substance misuse is an important target for prevention (University of Oxford).

In other words: the overwhelming majority of people with schizophrenia do not commit serious violence, and when risk increases it is often linked to factors that can be addressed, such as substance use and lack of treatment.

Persecutory delusions

What we are talking about

In everyday language people speak of "persecution mania". Clinically, several situations are distinguished:

Why it matters to investigators

It is a subject well known to anyone who works in an investigation agency. People sometimes come to an investigator convinced they are being followed, spied on, bugged: "tampered" phones, listening devices at home, cars following them, neighbours watching them.

It is a delicate situation that calls for balance and respect:

• Stalking and unlawful surveillance really exist. Since 1 January 2026 Switzerland has had a specific offence of stalking, Article 181b of the Criminal Code, punishable by up to three years' imprisonment and prosecuted on complaint, as reported by RSI, Swiss public broadcasting. A person who feels persecuted may be right, and must be taken seriously.
• It is not for the investigator to decide whether a belief is a delusion. It is not their job and they lack the competence.
• The investigator works on facts. They can objectively document what is happening and report honestly what they found and what they did not.
• They must not exploit vulnerability. Selling expensive, repeated checks to a person in distress, feeding their fears, is wrong. If the checks find nothing, that must be said clearly and tactfully.
• When suffering is evident, one can gently suggest talking to a trusted doctor. If there is a danger to the person or others, call 144 or 117.

The investigator's lesson. Faced with someone who feels persecuted, there are two opposite errors: dismissing them as "paranoid" without checking, or going along with them uncritically. The right path is the same as in any investigation: gather facts, document them, report them honestly. And remember that you are dealing with a person, not a case.

Narcissism

Trait or disorder?

"Narcissist" too has become an everyday insult. Psychology distinguishes between:

• narcissism as a personality trait, present to varying degrees in everyone;
• narcissistic personality disorder, a clinical diagnosis characterised by a pervasive pattern of grandiosity, need for admiration and lack of empathy, with significant consequences for the person's life.

Research also distinguishes grandiose narcissism, openly arrogant and dominant, from vulnerable narcissism, more hidden, hypersensitive to criticism and insecure.

What it has to do with investigations

In investigative work narcissism is often invoked in romance scams, manipulative relationships, business disputes or difficult separations. But a serious investigator never writes in a report that a person "is a narcissist". They describe facts:

Psychiatric labels in an investigative report are professionally improper, useless as evidence and potentially damaging to the reputation of the person described.

The rule against "diagnosis at a distance"

Psychiatry has a principle known as the Goldwater rule. The name goes back to 1964: during the US presidential campaign, Fact magazine mailed a questionnaire to more than 12,000 psychiatrists asking whether the Republican candidate Barry Goldwater was psychologically fit to be president. About a fifth replied, and 1,189 of them judged him unfit without ever having examined him. Goldwater sued for libel and won; the verdict was upheld on appeal in 1969.

In 1973 the American Psychiatric Association wrote the rule into its code of ethics as Section 7.3: a psychiatrist should not offer a professional opinion about a public figure without having examined that person and been granted authorization to make such a statement. The rule binds members of the American association and is still debated, as an analysis in the Journal of the American Academy of Psychiatry and the Law shows, but the underlying principle is simple: no direct examination, no diagnosis.

For an investigator it is not a written ethical rule but a rule of method, and the reasoning applies all the more: if a psychiatrist cannot do it, someone with no clinical training certainly cannot. In an investigation I can describe documented behaviour, that is, what a person did, when, and with what corroboration. Even the most careful criminological profile remains a working hypothesis, not a diagnosis and still less proof of guilt. Tools such as the PCL-R, after all, require an in-depth interview and a review of records by a trained professional.

Paraphilias and necrophilia

Paraphilia and paraphilic disorder

The DSM distinguishes between paraphilia, an atypical sexual interest, and paraphilic disorder, when that interest causes distress to the person or involves harm, or risk of harm, to others. Having a paraphilia does not mean committing a crime: the criminal issue arises when there are victims or breaches of the law.

Necrophilia

Necrophilia, sexual attraction to corpses, is among the rarest paraphilias and among the most studied in forensic settings precisely because of its gravity. The most cited study is that of psychiatrists Jonathan Rosman and Phillip Resnick, published in 1989, which analysed 122 cases drawn from the literature. According to the two authors, the most frequent motive was not sadism but the desire for a partner who could neither resist nor reject. A conclusion that shifts attention from monstrousness to these individuals' profound relational difficulties.

Legally, in Switzerland Article 262 of the Criminal Code punishes disturbing the peace of the dead, including desecration of a corpse. These are offences exclusively for the police and the judiciary.

I also wrote about this, from a historical perspective, in connection with Landru, the Bluebeard of Gambais.

Stalking: where psychology helps

Stalking is one of the fields in which psychology has produced useful tools. Australian psychiatrist Paul Mullen and colleagues proposed, at the end of the 1990s, a classification of stalkers based on motivation:

It is a useful classification for professionals who assess risk and support victims. But risk assessment in a specific case is for the police and specialist services. In a stalking case, the first step is to go to the police. An investigator can, in agreement with the victim and their lawyer, help document incidents lawfully.

Criminal profiling: between myth and science

The origins

Modern profiling was born in the 1970s within the FBI's Behavioral Science Unit at Quantico. Interviews with incarcerated serial killers produced, among other things, the famous distinction between organised and disorganised offenders. In Europe the British psychologist David Canter developed a more empirical approach in the 1990s, investigative psychology.

What the evidence says

Profiling has enjoyed enormous popularity thanks to books, films and TV series. Scientific scrutiny has been more severe:

• a meta-analysis by Brent Snook and colleagues, published in 2007 in Criminal Justice and Behavior, found mixed results on whether profilers outperform comparison groups, a very small number of studies and numerous methodological problems. The authors concluded that, until rigorous studies show otherwise, profiling should be viewed with great scepticism (Office of Justice Programs);
• the organised/disorganised distinction has been criticised because, in the data, many crime scenes show mixed characteristics.

What remains valid

This does not mean behavioural analysis is useless. It means it should be used for what it is:

I applied this cautious approach, for example, in the analysis of the Jack the Ripper case: a profile is a hypothesis, not a conclusion.

Mental disorders and criminal responsibility in Switzerland

A mental disorder can have criminal-law consequences, but not in the simplified way seen in films.

The essential point: it is not the diagnosis as such that counts, but the link between the disorder and the person's ability, at the time of the act, to understand and to control themselves. This is determined by psychiatric experts appointed by the authorities, not by investigators, journalists or commentators. The provisions can be consulted in the Swiss Criminal Code.

Under civil law

When a person, because of a mental disorder, cannot protect themselves or puts themselves at risk, Swiss civil law provides adult protection measures, up to placement for purposes of care under Article 426 of the Civil Code. In Ticino this is handled by the regional protection authorities. Again, this is not a task for an investigator.

The private investigator's role: what to do and what not to do

I dealt with vulnerable missing persons in the reconstruction of a 1736 case in the Bregaglia valley, and with psychological trauma in the article on post-traumatic stress disorder.

Myths and facts

In short

The human mind fascinates anyone who investigates, and it is right to understand it. But the first lesson of science is humility: labels simplify, profiles hypothesise, facts prove. A good investigator learns to tell these three things apart, and to remember that behind every diagnosis, and behind every suspicion, there is always a person.

If you or someone close to you is going through a difficult time, in Switzerland Die Dargebotene Hand / La Main Tendue / Telefono Amico answers on 143, day and night, anonymously. For children and young people there is 147. In an emergency call 144 or 117.

Main sources: American Psychiatric Association, DSM-5-TR (2022); World Health Organization, ICD-11 and fact sheet on schizophrenia; H. Cleckley, The Mask of Sanity (1941); R. D. Hare, Psychopathy Checklist Revised; D. L. Paulhus and K. M. Williams, "The Dark Triad of personality" (2002); P. Babiak and R. D. Hare, Snakes in Suits (2006); review of violence in schizophrenia published in JAMA Psychiatry (University of Oxford); J. P. Rosman and P. J. Resnick, study of 122 cases of necrophilia (1989); P. E. Mullen et al., typology of stalkers (1999); B. Snook et al., Criminal Justice and Behavior (2007); American Psychiatric Association, Principles of Medical Ethics, Section 7.3 (Goldwater rule); J. Kroll and C. Pouncey, "The Ethics of APA's Goldwater Rule", Journal of the American Academy of Psychiatry and the Law (2016); Swiss Criminal Code, Arts. 19, 20, 59, 64, 181b, 262; Swiss Civil Code, Art. 426.