THERE is a trend in certain scientific, medical and sociological quarters, to claim that much of human behaviour is predetermined by one or other of genetic, psychological, social, biochemical, environmental or even dietary ficors.
The current "guilty but insane debate in Ireland is an example of this. A particular example of the guilty but insane plea is the claim that violent criminal activity is caused by physical abnormalities in defined regions of the brain.
Society must be careful to place credence in these claims only in proportion to the strength of the evidence that the claims are true. In many instances, evidence in favour of such claims is flimsy or shaky.
If a person is convicted in our courts of a violent crime, but it can be shown that when the offence was committed the perpetrator suffered from a mental derangement, either temporary or of a chronic nature, to the extent he could not assess and weigh in a normal manner the consequences of his actions, then the court may absolve him of responsibility and declare him not guilty by reason of insanity.
A particular form of the guilty but insane plea becoming common in the US is the claim that physical abnormalities in certain regions of the brain can trigger uncontrollable violent behaviour in the individual afflicted - the neurological defence.
There is good evidence that this correlation holds true for at particular system in the brain called the limbic system.
Most neuroscientists agree that the limbic system is the seat of human emotions. A condition known as intermittent explosive disorder is generally agreed to be caused by seizures in the limbic system.
People who have this disorder suffer from intermittent paroxysms of aggression that usually dissipate as suddenly as they erupt. Generally, these episodes are not at all typical of the person's usual behaviour and character. Very often the individual remembers little or nothing of his actions, and when he does usually shows regret or self reproach. A young US Marine with this condition, fatally assaulted his lover. He recalled that she looked slightly different and the house smelled funny and be felt out of sorts. During an intimate moment in bed she made a funny remark after which he flew into a rage, choked her and slashed her throat. When he came to his senses he immediately went to law officers and admitted the crime, although he had no memory of his action.
The pattern of violent activity just described, associated with disorders of the limbic system, is well characterised and traditionally forms the firmest legal ground for a neurological defence.
In such eases also, EEG traces often display a noticeable abnormality originating in the limbic system. In the case of the young marine, when the court was convinced that he suffered from intermittent explosive disorder, the charge against him was reduced from first degree murder to voluntary manslaughter.
Emboldened by successful pleadings of the neurological defence in the ease of limbic system disorders, lawyers have begun to apply the neurological defence to murder cases that do not involve sudden outbursts of violence on the part of the defendant.
Even in 1968, before the condition of intermittent explosive disorder was identified, lawyers for Jack Ruby argued that his carefully planned murder of Lee Harvey Oswald was the result oft a minor epileptic seizure. This defence was unsuccessful.
For several years, Jeffrey Dahmer quietly lured to Milwaulkee residents into his house where he killed and cannibalised them. His crimes seemed especially deliberate and calculated. Dahmer's lawyers pleaded that their client was insane but a jury rejected this plea in 1992.
The evidence that abnormalities in the brain, in areas other than the limbic system, cant cause violent criminal activity is not strong enough to prove this connection.
What we are talking about here is the general mechanism responsible for motivation of our actions. This mechanism is surely likely to be complex and to consist of many factors that together contribute to determine the outcome.
At least some of the proponents of a widespread use of the neurological defence appear to be motivated primarily by a zealous opposition to capital punishment. Such people are not much concerned about the scientific validity of the basis of neurological defence and in practice are more concerned in making pragmatic choices of tactics that offer the client the best chance of avoiding the death penalty.
A general motivating factor underlying the advocacy of using the neurological defence on a widespread basis is a desire to excuse humans from responsibility for evil actions. This can bead to the use of circular arguments such as "no normal person could commit such a heinous crime - he must suffer from brain damage - the damaged brain caused him to commit the crime".
The impulse to absolve people of responsibility for evil runs counter to our traditional view of human behaviour where people act out of free will and must bear responsibility for the consequences of their actions.
While advocates of the new approach are eager to explain away badness I have never seen the model used to explain extraordinary examples of goodness, which would be an equally logical application.
THUS, for example, the actions of Mother Teresa are hardly "normal", but I have never heard it suggested that she acts out of uncontrollable impulses arising from structures in defined loci of her brain that are different from these structures in the average brain.
There is no doubt that in certain cases brain damage can cause violent criminal behaviour, e.g., disorders in the limbic system as described previously.
Bertrand Russell once wisely remarked that almost all problems in the world would disappear if people obeyed one simple rule, i.e., to rank the strength of their convictions in things directly in proportion to the strength of the evidence in favour of such beliefs.