Do your genes make you a criminal?

In the US a murderer is claiming his crime was the tragic consequence of being born a killer. Steve Connor reports on new arguments over whether some people are destined to be bad

Steve Connor
Sunday 12 February 1995 01:02 GMT

STEPHEN "Tony" Mobley has all the attributes of a natural born killer. Nobody could blame his upbringing - he came from an affluent, white, middle-class American family and he was not abused or mistreated as a child. Yet as he grew up he became increasingly violent, and at the age of 25 he walked into a pizza store and casually shot the manager in the neck after robbing the till and joking that he would apply for the job vacancy when the man was dead.

That was in 1991. Now Mobley is waiting on Death Row in Georgia to hear whether his appointment with the electric chair is to be confirmed. His last chance of a reprieve rests with a plea from his lawyer that the murder was not the evil result of free will but the tragic consequence of a genetic predisposition. The genes of Tony Mobley, his lawyers argue, meant he was born to kill.

The chief witness for the defence is Mobley's aunt, Joyce Childers, who has testified that various members of the Mobley family over the past four generations have inexplicably been very violent, aggressive and criminal, although most of them "mellowed" in middle age.

``There is no legal defence to his crime,'' says Daniel Summer, Mobley's attorney. ``There is only the mitigating factor of his family history. His actions may not have been a product of totally free will." Murder, rape, robbery, suicide, "you name it", the Mobley family has had it, he says.

The idea of invoking the Mobley genes as mitigation for the brutal murder of the pizza manager came to Mr Summer after reading about genetics research in the Netherlands. Scientists studying the history of a particular Dutch family had identified a specific genetic mutation that resulted in a chemical imbalance in the brains of some of the males in the family. This, they said, could explain why the same men were prone to unusually violent outbursts.

"We applied for $1,000 from the court to see if Mobley had a similar chemical imbalance, but we were refused. However, our appeal to the Supreme Court against the death sentence still rests on his family history of violent behaviour," Mr Summer says.

This week, at a closed meeting of scientists at the Ciba Foundation in London, Mobley's family tree will again come under intense scrutiny, this time by researchers studying the link between genes and violence. Deborah Denno, a genetics expert at the law school of Fordham University, New York, will end the conference by saying that it is not a question of whether genetic evidence will ever be admitted to court, but when and under what circumstances.

THERE is nothing new about the notion that criminals are born rather than made; it has cropped up repeatedly over the past century in the continuing debate over nature versus nurture.

This is, however, the gateway to a moral minefield. If it could be proved that the criminal urge might be traced to genes, then, some would argue, crime could no longer be blamed on parents, or society, or unemployment, or bad housing, or anything else that is capable of improvement. It would simply be a fact of life for which nobody was to blame, but which would be traceable to a minority of individuals.

This has uncomfortable overtones of eugenics, the pseudo-science which held that mankind could be improved by breeding out the bad, and which the Nazis took a step further by their policy of exterminating the Untermenschen. Even if it stopped there, the idea of the "criminal gene" would be controversial enough, but it does not, for modern science opens up new and different possibilities. If there are genes conferring on certain people a genetic predisposition to crime, could they and their carriers be identified, perhaps as early as the womb? What should happen to those embryos? Moreover, if someone is born with a criminal mind, what else should be done with them other than to lock them away for as long as possible?

The arguments date back at least to 1870, when Cesare Lombroso, an Italian doctor, devised his theory of the criminal man. The idea came to him in a "flash of inspiration" on a gloomy day in December when he was studying the skull of a notorious brigand: "At the sight of that skull, I seemed to see all of a sudden, lighted up as a vast plain under a flaming sky, the problem of the nature of the criminal - an atavistic being who reproduces in his person the ferocious instincts of primitive humanity and the inferior animals." Enormous jaws, huge eye sockets and handle-shaped ears were the sort of inherent features to be found in "criminals, savages and apes", Lombroso wrote.

Throughout the 20th century further attempts have been made to refine what Lombroso started. Many did little to improve on his nonsensical ramblings.

As recently as 1968, for instance, scientists thought they had stumbled across another physical marker for criminal behaviour. They found that 3 per cent of the male inmates in a hospital for mentally abnormal offenders had an extra Y chromosome. Enterprising lawyers seized upon this information and used it as defence evidence in court: "My client has the extra Y chromosome; he couldn't help himself." But it was soon discredited when it was shown that the majority of XYY men had no obvious abnormality and were no more likely to be involved in serious crime than normal XY men.

The more durable research into the genetics of crime has its roots in 1931, when psychologists began looking at nature's own "experiment" in genetics - twins. Identical twins share exactly the same genes, whereas non-identical twins share about 50 per cent of their genes, just like other brothers and sisters. Comparing the fates of pairs of identical twins and non-identical twins, it was clear, could offer some idea of how much a behavioural trait was due to genes (nature) and how much to upbringing (nurture).

Thus the results of twin studies have been at the forefront of the evidence for a genetic component to criminal and antisocial behaviour. Chief of these is the Danish twin study, which has been running for the past quarter- century.

Denmark has become a magnet for social psychologists interested in criminal genetics. Not only is it racially homogeneous, with a good health care system (both of which help to standardise data), but every pair of twins born since 1870 has been registered with the authorities, as has every criminal.

The Danish twin study has cross-checked criminal records for pairs of identical and non-identical twins to compare their fate. The broad conclusion is that a Danish man with an identical twin who has a criminal record is about 50 per cent more likely to have been in prison himself compared with the average Danish male. Non-identical twins are between 15 and 30 per cent more likely to both have criminal records.

Irving Gottesman, a psychologist at the University of Virginia who has worked on the Danish twin study, believes the results show that "criminals are not born, but the odds at the moment of birth of becoming one are not even".

Another Danish study, this time of identical twins who are reared apart in different families, appears to support the notion of being born with a criminal disposition. According to Sarnoff Mednick, a psychologist at the University of California at Santa Barbara, a child whose biological parents are criminals is more likely than other children to begin a criminal career himself even if his adopted parents are law abiding.

Yet another Scandinavian adoption study, this time in Sweden, found a link between criminality, genes and alcohol abuse. Michael Bohman, professor of child psychiatry at Umea University, says the results show a clear genetic predisposition to alcohol abuse which leads to a rising tendency towards anti-social or criminal behaviour. "Of course if there was no alcohol in the environment then there would be no alcoholism," he says. "The risk is related to your genes and the amount of alcohol you're swimming in, but not everyone, of course, drowns."

Studies on twins and adopted children have always suffered from a basic problem. They can only indicate a possible genetic component to a trait. They cannot find the genes involved, nor can they say much about the mechanisms by which environment or upbringing could overcome the genetic predisposition. Every geneticist knows that even if a trait is 100 per cent genetically determined, that does not necessarily mean that nothing can be done about it. The classic example here is the inherited disease phenylketonuria, which can lead to mental retardation. A simple change in the infant's environment, in this case a diet free of the amino acid phenylalanine, can completely override its genetic "destiny" and the disorder is overcome.

The history of studies such as these, especially in relation to the debate over IQ and genetics, is littered with controversy. Conclusions from such work have usually been fiercely challenged and some have had to be withdrawn after other researchers had identified methodological flaws. Today, however, there is a new dimension.

ALTHOUGH twin studies go on much as they always have, genetics has become transformed over the past 10 to 15 years. New techniques in molecular biology have enabled scientists to identify specific inherited defects in DNA, the genetic blueprint. One of the most startling pieces of research into the genetics of violence has come out of the Department of Human Genetics at the University Hospital in Nijmegen. This was the work that inspired the unusual plea of mitigation from Tony Mobley's lawyers.

The scientists at Nijmegen studied the apparent inherited aggression of the Dutch family. Han Brunner, who led the research team and who will also be attending this week's Ciba conference, has, however, distanced himself from suggestions that he has found a "gene for aggression".

"The notion of an `aggression gene' does not make sense," he says, and it would be wrong to suggest that any one gene or collection of genes can account for something as complex as aggressive human behaviour. He emphasises that his research has only demonstrated how a very specific genetic defect can result in a fairly specific behavioural abnormality in one particular family, not society at large. The family spanned four generations and almost a century in time. He found that at various times 14 men in the family had displayed mental retardation combined with unusually aggressive posturing, verbal abuse and sometimes physical violence. There was one instance of rape, two of arson and one of attempted murder.

Professor Brunner's investigation soon found that the trait was "sex linked" like the blood disorder haemophilia, which affects only males but is transmitted through the maternal line. Further work identified the gene itself, which is responsible for an enzyme called monoamine oxidase- A.

Defects in the gene of the aggressive men prevent the enzyme from working, so causing a build-up of neuro-transmitters in the brain, perhaps resulting in over-excitation of the nerves in stressful situations.

Although this sounded a neat solution to the problem, Professor Brunner was presented with some logical inconsistencies in that drugs blocking monoamine oxidase-A have been used extensively to treat patients with depression, with no apparent increase in violent tendencies. Furthermore, one of the neurotransmitters building up in the men was serotonin, which other researchers have found to depress, rather than increase, the propensity for aggression.

Such contradictions serve to reinforce the difficulties of explaining complex emotions in biological terms. Nevertheless, psychologists keep pointing to a clear biological basis for criminal or antisocial behaviour on the basis of their studies on twins and adopted children.

Even if there does appear to be a genetic basis to some types of behaviour that lead to criminality, psychologists are almost unanimous in their belief that it does not mean some children are doomed to a life of crime. "Just because it's genetic it doesn't mean to say it's not amenable to environmental intervention," says Judy Silberg, a clinical psychologist at the Virginia Commonwealth University. "If weapons are available and you have kids with, say, attention deficit disorder, it's a set-up. You're setting up a situation to happen."

THERE are some bitter opponents of what has become known as "neurogenetic determinism". Steven Rose, a brain researcher at the Open University, is a long-standing critic of those who believe that individual differences in human behaviour, notably IQ, have a genetic rather than environmental basis.

He lambastes the "reductionists" who believe there is a raw genetic basis for criminality and violence. The rise in genetic determinism offers no solutions to what are essentially society's problems, he wrote this month in the journal Nature.

"Although only the most extreme reductionists would suggest that we should seek the origins of the Bosnian war in deficiencies in serotonin-reuptake mechanisms in Dr Karadzic's brain, and its cure by the mass prescription of Prozac, many of the arguments offered by neurogenetic determinism are not far removed from such extremes."

Professor Rose is particularly scathing about a recent attempt by some US researchers to establish a "violence initiative" which would investigate the biological basis of ghetto crime. "As an approach to diminishing the violence of city streets, it would seem unlikely to achieve as significant an impact as would measures to reduce the estimated 280 million handguns currently in personal possession in the United States."

This issue excites strong emotions. Two years ago there was public outrage in the US over a federal anti-violence initiative, conceived by Louis Sullivan, a black physician and then secretary of the US department of health and human services. The idea was to help young black people, who are disproportionately involved in violent crime. Part of the initiative involved investigating the ``biological'' basis of violent crime.

Civil rights leaders and others became deeply suspicious, especially after one leading scientist cited monkey violence and sexuality as the research rationale. "Maybe it isn't just the careless use of the word when people call certain areas of certain cities `jungles'," he said. Amid uproar, the project was shelved.

The notion that crime, genetics and race might be linked has particularly inflamed both proponents and opponents of "genetic determinism". Because skin colour is a genetic trait, because crime statistics show that blacks are more likely to end up in jail than whites, and because an increasing number of researchers appear to believe in a genetic basis of crime and violence, some commentators have jumped to the conclusion that black people are more likely to be involved in crime because of their genes.

The water has been further muddied by the recent publication in the US of a book called The Bell Curve by two right-wing social scientists, Richard Hernstein and Charles Murray. The book argues that IQ has a genetic basis and this accounts for an inherent difference between the IQs of the races. Low IQ people, the book says, are more likely to commit crimes because they lack foresight and cannot understand that robbing someone is wrong.

Few, if any, of the psychologists and geneticists at this week's Ciba conference would agree with Hernstein and Murray. They might, however, be persuaded that cold-blooded murderers such as Tony Mobley can have a genetic predisposition to violence and antisocial behaviour which they are born with.

The problem for Mobley, and others like him, is that judges and juries may be all too ready to agree and conclude that the only treatment is to lock them up and throw away the key, or, in the case of Mobley, throw the switch on the electric chair.

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