Crime, a major London conference will hear next week, could be in the genes. As the argument that some people are biologically disposed to criminal behaviour has gained ground, Kam Patel asks academics for their views and the implications for the legal system.

Next Friday marks the fourth anniversary of the murder of John Collins at Domino's pizza parlour in Oakwood, a small, quiet town in Hall County in the state of Georgia.

After a delay of three years, the trial of his murderer, a 29-year-old white, Tony Mobeley, took place last February. He was found guilty and sentenced to death. Many at the district attorney's office cannot recall ever having to deal with anyone quite like Mobeley. According to Lee Parks, assistant district attorney in Hall County, Mobeley took to decorating his cell with Domino pizza boxes, bragged to fellow inmates about the killing and carried a one-two domino piece (the Domino logo) as a "good luck charm". Mobeley even had dominoes tattooed across the back of one of his shoulders, says Parks.

But what appears to be pretty much an open and shut case - even Mobeley has never denied his guilt - has been catapaulted on to the battlefield of a fierce worldwide debate. For Mobeley, in an effort to mitigate his sentence to life, claims that his genes made him kill the 21-year-old Collins. He is arguing that he has inherited a genetic condition that makes it difficult for him to control violent, impulsive behaviour and wants to have a scientific test to prove it. So far the request for state funds to have the test has been denied. A final decision by the state supreme court is imminent.

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To back up their calls, Mobeley and his lawyers have exploited to the full a remarkable study carried out by a team of scientists on a large Dutch family in which several males are said to be affected by borderline mental retardation and abnormal behaviour including marked criminal activity. The scientists claim to have identified a defective gene that normally regulates the production of chemicals that play a vital role in the transmission through the body of electrical impulses or messages associated with aggressive behaviour.

The judge in Mobeley's case did not argue with the findings but noted the researchers' warning that the results applied to just one family and should not be extended to society in general. But as a foretaste of the huge legal problems should genetic predisposition data ever become widely admissable, the judge pointed out that even if the test was allowed and the results supported Mobeley's claims, mechanisms do not exist to deal with such evidence.

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Lydia Sartain, district attorney at Hall County, is under no illusion about what the future might hold: "At present I have serious reservations about the scientific data. But if at some point down the road it becomes irrefutable, then we would have to consider seriously admitting it as evidence. The American legal system is very fluid and I believe the changes could be made to accommodate genetic data. But the repercussions will be enormous. We would need to have a national debate on the social implications and its impact on the criminal system."

Han Brunner, based at the department of genetics, University Hospital in the Netherlands and one of the researchers involved in the Dutch study, willbe speaking next week in London about the work at a CIBA Foundation conference in London on the genetics of criminal and anti-social behaviour. One of his points is that the findings of the research relate to just one specific observation. He says: "You definitely do not want the results to be generalised for society. The findings have not been replicated elsewhere as far as I know."

Like many other scientists working in the field, Brunner is acutely sensitive to the use of such data. He says: "Nothing is simple. You may have good statistical correlations in an experimental setting but in real life there are too many other factors to have just a deterministic, mechanistic or even a probabalistic answer. I think that what is going to happen is that once the genes have been found, people are going to realise that it is both genes and environment that contribute. " And indeed, even as the data continue to accumulate, very few scientists working in the field are claiming that "criminality is all in the genes". For the "believers", determining how much weight to attach to genetic data in relation to environmental factors and developing an understanding of how the two interact are crucial.

But there is fierce criticism from scientists such as Steven Rose who believe that the basic data is fundamentally flawed. Detractors are also deeply concerned, for example, that with increasing public concern about violent crime, such data could easily become a convenient means of justifying social policies that substantially downgrade environmental considerations such as poverty and ill-health. Afro-Americans, for example, are heavily over represented in prisons. Could misuse of genetic data work against them? Another fear is that genetic predisposition data could be used by prosecutors as a means of predicting guilt or likely (scientific) guilt rather than determining it using conventional investigative procedures.

While next week's conference, to be chaired by Sir Michael Rutter of the Institute of Psychiatry, will deal with some of these issues, the event will also be notable for sending out the message that a "new wave" of genetics research is firmly established. This new genetics aims to show that it is trying to find genes to help explain criminal and anti-social behaviour.

Robert Plomin, MRC professor at the Institute of Psychiatry, also rejects the charge that much of the scientific work being done in the area is blatantly reductionist. "That people do not exhibit behaviour unless they have genes is a truism. A hollow truism. But it is not about whether we can reduce the whole thing to genes. The real issue is explaining the difference between individuals. We need a balanced approach to what the behaviourists, psychiatrists, molecular biologists and environmentalists have to say.

"The way forward is to incorporate genetics data into environmental research. We should not be saying that it is all genetics and the rest is junk."

But much will depend on environmental researchers who, in the past, have been reticent about taking on board genetic data. "They might make a lot more progress if they did," says Plomin.

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Crime, a major London conference will hear next week, could be in the genes. As the argument that some people are biologically disposed to criminal behaviour has gained ground, Kam Patel asks academics for their views and the implications for the legal system, while Adrian Raine and Steven Rose (opposite) put the case for and against a genetic view of crime Suzanne Gibson

"Our gravest error would be to confuse the law with the truth. Law exists to apportion responsibility, resources and risk among its subjects. In doing this, law's task is not to mirror the world but to manage it. What we call justice is our judgement on law's adjudications in the flickering light of our favoured beliefs, Christianity, Marxism, feminism, racism or what you will. Beyond adding a new 'ism' to the justice debate, will geneticism make any difference?

"If we continue to believe that it is wrong to thieve or murder, the discovery of a genetic basis to such behaviour should have little impact upon law itself. The criminal law declares a man guilty where he intentionally commits a criminal wrong. But the legal concept of intentionality would collapse under examination by a competent Freudian, and would acquit itself no better in cross-examination by geneticism. We keep it only because it is convenient. If geneticism came up with some better rule of thumb, law might adopt it. But not because it is true.

"Might law itself be explicable as genetically structured social behaviour? It is not unusual for theorists to claim that legal outcomes have something to do with matters other than those apparently in hand. Marxists argue that legal decisions reflect bourgeois priorities, feminists that they encode patriarchy and legal realists that they depend on what the judge had for lunch. The coming of a genetic account of the content of criminal or civil law is only to be expected. More novel is the suggestion that the deep structures of law are a biological phenomenon. I have surveyed the sociobiological arguments, the most interesting of which is that the human mind has evolved to possess an aptitude for justice. But little work has yet been done; genetic jurisprudence lies (if anywhere) in the future."

Suzanne Gibson is fellow and tutor in law, New College, Oxford.

John Hapgood, Archbishop of York "From a theological perspective one of our key attributes as human beings is our capacity for self-transcendence. Human nature is open-ended. Though we may be constrained by circumstances, we nevertheless have the freedom to make real choices, and the possibilities of freedom are enhanced as we take responsibility for them.

"Such a theological understanding of human nature is perfectly compatible with the belief that many of our capacities and predispositions may in some way be determined by our genes. Twenty years ago the sociobiologists began studying hereditary dispositions from an evolutionary perspective, and set the scene for a comparative study of human and animal behaviour. It is clear from such studies that whatever may be inherited is profoundly influenced in its mode of expression by cultural and personal factors. It also looks as if basic capacities are more directly heritable than personality traits.

"If this is true of studies which take account of the complex interactions between many genes, it is likely to be even more true that individual genes cannot be held responsible for specific forms of behaviour. Individuals are much more than their genes, and a simple reductionist approach to one of the most fundamental aspects of human personality, the capacity for moral choice, seems to me both scientifically implausible and humanly disastrous. The idea for instance, that original sin might somehow be related to genes which predispose to aggressive behaviour, demonstrates the kind of muddle to which such thinking can lead.

"Original sin is a description of our innate self-centredness. This is aggravated by cultural factors as the wrongs done by one generation are passed on to the next. It is the void waiting to be filled by the grace of God, and the damage waiting to be healed by the love of God. Essentially, therefore, original sin is about our dependence on God for our full humanity. At times this separation from God can show itself in aggression, not least because psychologically aggression is often related to a form of dependence which has gone wrong. But to identify that with a genetic predisposition is simply to spread confusion."

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Richard Dawkins

Reader in zoology at Oxford University

"To blame your crime on your genes is no more, and no less, sensible than to blame it on your brain or on your infant nanny. In an unhelpful sense, everybody's deeds are caused by events in the past. So what? This has never stopped laywers attributing blame and responsibility to individuals. Lawyers and judges should not be duped into thinking that genes are inherently more 'deterministic' than environmental factors."

John Krebs and Alex Kacelnik

John Krebs is chief executive of the Natural Environment Research Council and Alex Kacelnik a lecturer in zoology, Oxford University.

"The debate about genetic differences in behaviour between individuals, or groups is not about whether such differences exist, for this is an undisputed fact. The debate is about three things: the kinds of behaviour for which genetics may influence individual differences; the relative importance of genetic and environmental differences; and whether or not genetic differences are ineluctable (the hypothesis of genetic determinism).

"Behaviour is merely one expression of an individual's biochemical, physiological and anatomical make up, so virtually any measurable genetic difference between individuals can be expressed as a difference in behaviour. A trivial example: a genetic difference between individuals (or between populations such as Swedes and southern Italians) in leg length results in a behavioural difference in stride pattern. Some differences in leg length between individuals or populations are attributable to genetic differences, so differences in walking behaviour are also genetic.

"But what about more 'complex' patterns of behaviour, such as playing the piano, teaching philosophy or mugging old ladies? The same argument applies. Differences in hand size are partly attributable to genetic differences, so variation in piano-playing ability is at least to a degree genetic. In short 'genetic variation in behaviour', even complex behaviour, may be no more than variation in bone length, cell membrane properties, and so on.

"The relative importance of genetic and environmental variation is sometimes expressed in an oft-misunderstood measure called 'heritability'. To say, for example, that the heritability of IQ is 80 per cent does not mean that within an individual the level of IQ is 80 per cent genetic. It means that differences between individuals are 80 per cent genetic. The value of heritability depends on the environment in which you measure it. In theory it is possible to raise a group of children in absolutely identical environments, in which case any differences in IQ would be genetic: heritability would be nearly 100 per cent.

"If the same children were raised, some in favoured and some in deprived conditions, most of the variation between them in IQ would be environmental: heritability might be near zero. Assertions about heritability, especially when applied to differences between groups raised in different environments, should be treated with caution.

"Genetic differences between individuals can often be modulated or entirely eliminated by environmental influences. A clear example is the debilitating disease phenylketonuria which is due to a simple genetic difference but can be totally eliminated by diet.

"In other words, acceptance of the fact that behavioural differences are influenced by genes is far from a doctrine of genetic determinism - the view that genetically determined effects cannot be motivated by the environment. In fact, the recognition of genetic differences may be the best guide to treatment by environmental modification."

Mary Warnock

"If empirical research pursues the link between the presence of a particular gene, or set of genes, and violent, anti-social behaviour, and successfully identifies such a link, then philosophy will have to come behind, tidying up the resultant chaos. The chaos will be in the conceptual framework within which we think of behaviour that is damaging to individuals and society, in other words our concepts of morality. This is nothing new. To use a moral vocabulary, of righteousness and sin, temptation and the overcoming of temptation, virtue and vice, is to assume both that people are more or less responsible for what they do, and that some kinds of behaviour are not only more socially acceptable, but better than others, an ideal to be pursued.

"Moral condemnation or punishment manifestly does not work, and in any case sticks out like a fundamentalist sore thumb in a general sea of relativism. It is easy to say that we must be 'non-judgemental'. Yet there is a justified fear that if the language of morality is abandoned, people will get worse, more greedy, more violent, less to be trusted.

"We want to believe that people are responsible and can improve themselves if only they are enabled to, by education and example. To believe anything else is to diminish our respect for humanity, and what it is capable of. To say of a violent and aggressive person that he can't help it is immediately to designate him an object, a fit subject for treatment not conversation, inferior to the doctor or psychiatrist who is going to try to change him in desirable ways. Genetic manipulation of people thought to be likely to offend raises still more urgently the questions who decides, where does the norm come from, what genes are to be "treated", what are to be left alone?

"I am sure that research on these issues must go on. I am equally sure that the links will turn out to be obscure, the effects of environmental influences incalculable. If this is so, we shall perhaps gain not only knowledge (worth having for its own sake) but also the wisdom to recognise certain limits to physical intrusion into the human personality, and so to put more of our resources into education, rather than medication or surgery."

Philosopher Mary Warnock is the former mistress of Girton College, Cambridge.

Michael Rutter

"The genetic study of anti-social behaviour should have practical benefits because the findings will aid our understanding of its causes. This is crucial for the development of effective means of prevention or alleviation. In order to understand what can be accomplished, a few common misconceptions must be disposed of. Nongeneticists sometimes assume that the goal is to determine how much of a disorder is due to genetic factors and, if the answer is 'a lot', that must mean that environmental measures will be of little value.

Nothing could be further from the truth. Quantification of the genetic component is of very limited use on its own. On the other hand, quantification is useful as a first step towards the goal of understanding how genetic and environmental risks work. Moreover, a very strong genetic influence does not imply that environmental intervention will be ineffective; all depends on the genetic mechanisms.

"People are also sceptical for a different reason; namely that because crime is legally determined, and because anti-social behaviour is socially defined, it is quite implausible that there could be a gene for "crime". Quite so. But therein lies one of the main uses of genetic research. Anti-social behaviour is both extremely common and quite varied. Most 'crimes' are relatively trivial acts committed by teenagers who grow up to be unexceptionable citizens in adult life. But some anti-social behaviour begins early in childhood, is associated with widespread social malfunction and persists into adult life as some kind of personality disorder. Research findings available so far suggest that the former (transient adolescent juvenile delinquency) is mainly environmental in origin, whereas genetic factors are much more important in the latter, probably through their role in early onset pervasive hyperactivity.

"The last point is critical; the main value of genetic research is in the determination of how the genetic risk operates. The next question is whether personal qualities predispose to anti-social behaviour only if there are also environmentally mediated psychosocial risk factors. Molecular genetic studies will be important in answering those questions because the genetic contribution can be identified rather than inferred, and because this will enable the interplay between nature and nurture to be investigated directly."

Michael Rutter is professor of child psychiatry at the Institute of Psychiatry, University of London.

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