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Why do some serial killers enter an insanity defence plea?

Inside Bedlam, scene from William Hogarth's A Rake's Progress (1735) (Public Domain)

In my YouTube channel, Micki Pistorius Profiler on Record, (episode 3) I discuss why some serial killers – and other criminals – enter an insanity plea, claiming not to be of sound mind, or to suffer from a mental illness in order to escape prosecution. The secondary gain of escaping criminal liability is a common motivation for malingering – pretending to be mentally ill.  However, criminals often do not comprehend that even if they are found incompetent to stand trial, the charges will not be dropped – they will be kept in psychiatric custody until they are found fit to stand trial. When entering an insanity plea, or if a judge suspects that the accused may suffer from some mental incapacity, he / she is referred to a state psychiatric facility for observation.

Once in psychiatric custody of the state, they can be subjected to psychometric tests and observation by parties whose interests are not aligned with that of the accused.  Also prolonged psychiatric custody might even outrun the time of a convicted sentence as was the case of Dimitri Stafendas who assassinated the prime minister of South Africa, Dr Verwoerd in 1966. Stafendas was 44 when he committed the crime, at the age of 81, he died of pneumonia in October 1999, 33 years after the assassination. Had he not died, he would still be kept “at the pleasure of the State President”. So, an insanity plea might not in the long run benefit the accused. There may be some indications of mental illness, but these may be found not to interfere with the accused’s ability to stand trial.

Forensic psychologists can determine if someone is malingering (pretending) by various methods, such as interviews over time, psychometric tests and hypnosis. To ensure unbiased procedures, academic experts are requested to hypnotize suspects and the process may be videotaped to illustrate no undue influence. People who have known the accused for a long time may also not report any bizarre behaviour, clearly indicating malingering. True amnesia or memory loss, usually has a long history, which cannot be conjured up just before a trial. 

It is quite common for criminals and serial killers to claim to be suffering from Multiple Personality Disorder – the correct term being Dissociative Personality or Identity Disorder.  In America Kenneth Bianchi, one of the Hillside Stranglers tried this, unsuccessfully. If there are multiple personalities, they are insulated from each other and they do not switch upon cue. Dissociative Personality/Identity Disorder is an extremely rare phenomenon – in my 30 years as a psychologist I have only encountered one true case, and this was in a clinical setting, not a forensic one. The success rate at faking it would be close to zero.

During one of the trials I testified that people who suffer from Dissociative Personality/ Identity Disorder supress and internalize their extreme childhood traumas to such an extent that the ego may develop alter-ego’s, as a defence mechanism.  The ego’s of serial killers, on the other hand find retribution in acting out their vengeful fantasies – so the two are incompatible.  My testimony was challenged by a colleague, but the judge accepted my testimony and the accused whose case I was testifying was eventually found guilty of rape and two murders and sentenced to 99 years.

Section 77 and 79 of Criminal Procedures Act 1977 of South Africa states: The accused may be found mentally ill or not mentally ill, fit to stand trial or not fit to stand trial, to have the capacity to appreciate the wrongfulness of the act in question and to act accordingly or not, and to be found mentally ill or not mentally ill at the time of the offence. So when they plead an insanity plea the first element to establish is whether they are fit to stand trial, and then whether they could appreciate the wrongfulness of their act, and act accordingly at the time of committing the act.  So note there are two time periods here – the time when the accused committed the act and then when it is time to stand trial.

Even if an accused was mentally ill before and after the act, and they committed the crime during a lucidum intervallum (sane interval), they are criminally responsible for the act. Mentally ill persons can have interim periods of sanity.

There are also the pleas of pathological and non-pathological incapacity. In the case of non-pathological incapacity, the accused alleges that at the time of the commission of the crime the accused lack criminal capacity that was not due to a pathological disease. For example the accused was under such emotional stress that they could not appreciate the wrongfulness of their act, although they did not suffer from a mental illness.  For example a father killing the rapist of his child in anger.

If this defence is used, the state bears the onus of proving beyond a reasonable doubt that the accused had capacity at the time of the crime. However the accused must lay a foundation for his defence, which is sufficient to create a reasonable doubt. The courts do not take this defence lightly and take great care to scrutinize the evidence.  For example the court will take in to consideration the duration of the emotional stress building up to the act.

In the case of a pathological incapacity, the defence attorney of the accused would bear the onus of proving that at the time of the commission of the crime the accused lacked criminal capacity on a balance of probabilities and that the accused has clearly been found mentally ill.

Automatism, is another defence which deals with involuntariness. Involuntariness refers to the accused conduct at the time of the commission of the crime. The accused is said to have acted involuntary if his conduct was not subject to his or her conscious will. For example, someone had an epileptic fit – involuntarily – and drove over a pedestrian (however in this case the question would be if the person should have been driving), or the person was influenced by medication.

Insanity pleas is a catch phrase for many possibilities, but the courts do not take these lightly and many criminals believe an insanity plea could be their Get-out-of-jail-free card. They could not be more wrong!

Featured image: Inside Bedlam, scene from William Hogarth’s A Rake’s Progress (1735) (Public Domain)

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