The practice of forensic medicine

The practice of forensic medicine

The practice of forensic medicine (medicinaforensis) is largely focused on the clinical aspects and pathology of medicine as they relate to the needs of the courts of law [forensic (adjective) = of courts of law].

The terms ``forensic medicine'' and ``medical jurisprudence'' are often used synonymously, but in fact differ in meaning. ``Medical jurisprudence'' is sometimes used in a wide sense as also inclusive of medical law, in other words the law pertaining to the practice of medicine, while ``forensic medicine'' refers to the ``medical'' needs of the courts.

Clinical forensic medicine embraces the medical condition of the living ``victim'' and/or ``assailant'' arising out of assault and alcohol and drug usage, as well as topics such as age determination, identity, abortion, sexual offences and iatrogenic conditions (``iatrogenic'' means ``resulting from the activity of doctors'').

Forensic pathology, on the other hand, involves largely the post-mortem medical investigation of deaths which appear to be the result of causes other than natural causes. It also involves pathology laboratory procedures and investigations needed to support both clinical forensic medicine and the post-mortem investigation. This includes, for example, microscopic examination of tissue, microbiological and biochemical tests and blood and tissue grouping.

Further support to both the clinical and pathology investigations is offered by the analytical toxicologist who undertakes tests for the determination of foreign chemical substances in body tissues and fluids. Not infrequently the medico-legal investigation becomes a multi-disciplinary team-effort on the part of a number of different categories of scientists, which may include the forensic psychiatrist, odontologist, biologist, ballistic and other forensic scientists of many different callings.

[The following need not be studied for examination purposes.]

In his inaugural lecture delivered at the University of South Africa in 1976 the late Professor HA Shapiro addressed himself to the practice and scope of forensic medicine. A slightly abridged version of his address follows:

The scope

Forensic medicine includes every aspect of medical practice which can assist the courts in resolving an issue. There is a considerable civil sphere, arising largely from non-fatal traffic accidents, in which any medical practitioner may become involved as an expert at any time, in his capacity as a physician, a neurosurgeon, a neurologist, a psychiatrist, an orthopaedic surgeon, and so on.

Here I include those medical examinations of persons alleged to be under the influence of alcohol or other drugs; of assailants and victims in cases of assault, including rape, etc. This kind of medico-legal examination is an ordinary general clinical examination which all medical practitioners are trained to do. In examining a person alleged to be under the influence of alcohol or drugs, the emphasis would be on the reason for a transitory disturbance of the nervous system. No special merit resides in the examination or the opinion merely because it has been made by a district surgeon.¹ In this, as in all cases, it is the reasons for coming to a conclusion that will, in due course, be scrutinised and tested in cross-examination in court. Whether the expert is a district surgeon or a specialist, nothing can avail him in these circumstances except his clinical competence, derived from his general medical training and experience.

The practice

But there remains a field requiring knowledge which is not ordinarily within the province of medical practitioners unless they have been exposed to a special kind of training and experience. This is the area we can conveniently describe as falling within Forensic Pathology. It is easier to describe than to define Forensic Pathology, which is concerned largely with deaths not due to natural causes. It includes a study of the fatal effects of poisons, under the title of Toxicology.

There is sometimes a tendency to argue that an external examination of the body reveals such severe injuries as to make a post-mortem examination unnecessary. This attitude embraces the fallacy of accepting the obvious. The need to do a careful post-mortem examination, despite what common sense may dictate to the contrary, is well demonstrated in the case of Rex vBlom. This case, as you all know, stresses the 2 cardinal rules of logic which cannot be ignored when reasoning by inference:

·              The inference sought to be drawn must be consistent with all the proved facts. If it is not, the inference cannot be drawn.

·              The proved facts should be such that they exclude every reasonable inference from them save the one sought to be drawn. If they do not exclude other reasonable inferences, then there must be a doubt whether the inference sought to be drawn is correct (1939 AD 188, at 202±203).

In this case the body of the deceased had been mutilated by a train which had passed over it. The post-mortem examination yielded evidence which was consistent with the view that the deceased was dead before her body was placed on the railway line and that she had been killed by an administration of chloroform. This case strikingly demonstrates the importance of a careful post-mortem examination on all occasions.

The forensic pathologist is, however, also confronted, to a considerable extent, with deaths due to natural causes, but occurring in such circumstances that the usual death certificate cannot be issued by a registered medical practitioner.

In actual practice, therefore, an inquiry into the cause of death requires, to begin with, an adequate knowledge of the abnormal signs encountered in deaths due to natural causes. At the time of the post-mortem examination an investigator cannot, in many cases, be sure in which category the death will fall.

The limitations on the inferences which can reasonably be drawn from isolated, naked-eye post-mortem findings must be appreciated very clearly. Nowhere are these limitations reflected better than, for example, in deaths where an anaesthetic has been administered: in cases of fatal poisoning, where it is the negative findings which should raise suspicion: in many cases of head injury and in many deaths due to natural causes. The problem arises regularly where death is attributed to arteriosclerotic heart disease on the basis of the solitary post-mortem findings. The deceased, after all, had been walking around, harbouring his disease, until just before he died.

There need and should be no hesitation about declining to state the cause of death on the post-mortem findings alone, when the autopsy observations clearly do not permit the pathologist to do so. He may only be in a position to give the answer when the results of other investigations are made available to him, eg a clinical history of the case, the results of a toxicological or other laboratory analysis, etc. The pathologist then acts as a consultant and expresses an opinion on all the facts when these are put to him at the proper time and in the proper place, eg in an inquest court or during a trial. The post-mortem examination is really just a special investigation and is only one of the items in the total collection of evidence which must be evaluated in coming to a conclusion. It is important not to confuse the role of the consultant with that of the observer carrying out the autopsy. Two separate operations are involved in coming to a diagnosis.

The forensic pathologist cannot, however, express such a view without relying on a general knowledge of medicine, which must be applied to the circumstances of a particular case. This contribution is best made by those who are, to begin with, well trained in all branches of medical knowledge. This emphasises the need to ensure that he is, in the first place, a competent medical practitioner. Any defects in his medical knowledge must inevitably be reflected in the inadequacy of his opinion as a medico-legal expert.

There seems to be a view, which is fairly widely held in some quarters, that the performance of a post-mortem examination necessarily provides the answer to the cause of death. In fact, this is so only in a relatively small percentage of cases in which the lesion observed is incompatible with life.

There is no reason for a medico-legal pathologist to feel obliged to pretend to omniscience or papal infallibility. It may well be a matter of regret that post-mortem findings are not always capable of providing those precise answers which legal questions so often demand. But this is not the fault of the medical witness, who must consequently guard with great care against pretending to a knowledge which, in the nature of things, he cannot have. Should he make such claims, he would merely demonstate that he stands alone in the possession of unique talents which his colleagues in the rest of the scientific world lack.

There is no duty upon him to become a kind of sniffing medical bloodhound who naõÈvely considers it a compliment to be described as wearing the mantle of a Spilsbury; nor can we allow Forensic Pathology to descend to the level at which the pathologist may have to be equated in status with the ancient Roman augur who, with prophetic insight, offers his soothsayers's opinion after inspecting the entrails of a corpse. It is a matter of some concern that many a forensic opinion in medico-legal pathology has virtually not advanced beyond the stage of such ancient Roman quackery.

The unavoidable shortcomings in medical knowledge emphasise the importance of instructing legal practitioners in the principles which should guide us all in evaluating the observations made by practitioners and the legitimate inferences they seek to draw from them.

Ex Africa semper aliquid novi

Now it so happens that in South Africa all medico-legal post-mortem examinations are carried out exclusively by employees of the State. They are the only medical practitioners who are exposed to this kind of medico-legal experience. It is therefore gratifying to know that from their ranks have come research workers whose contributions have profoundly influenced the teaching and practice of Forensic Medicine all over the world.

Perhaps the single, most fundamental and revolutionary contribution burst upon the scene when, on 9 September 1944, Professor I Gordon published a paper entitled A Classification of Deaths of Medico-Legal Importance, in the British Medical Journal. Professor Gordon used to be a senior academic in this field and his paper (written with Einsteinian conciseness and brevity) was merely the forerunner of a series of observations which had 3 main consequences. His work produced a startling impact on the practice of our discipline; it rescued Forensic Pathology from the Cinderella role which had overtaken it; and it ushered in a scientific era in the history of Forensic Pathology. South African medico-legal research thus came to influence forensic teaching and practice far and wide.

Alexander Pope has reminded us that the proper study of mankind is man. As I will demonstrate, the proper studies which come from South Africa contributed to a scientific evaluation of many problems that face us daily. The research work was marked by its utilitarian character. This is not to say that we are unsympathetic to fundamental inquiries which have no immediate practical application  -   what we may call futilitarian research. Indeed, some of my best friends in research are futilitarians! But the nature of the problems which confronted us impressed on us the immediacy and the urgency of the need to examine these practical issues. The liberty, if not the lives, of accused persons were at stake because so-called expert opinions were being offered which were without any scientific foundation and which reflected the ignorance, the obstinacy, the bias and prejudice of those who are not handicapped by a knowledge of the subject.

As you can well appreciate, a very considerable part of our practice is concerned with violent deaths, eg deaths due to suffocation, throttling, strangling, hanging, drowning, etc. These are the so-called asphyxias, where death is due to a mechanical obstruction of the airway. Those who taught us and wrote the textbooks on which we depended, led us to believe that it was possible, on the basis of the post-mortem findings alone, both to recognise that death was due to asphyxia and to determine its particular type. These assertions are still made in some quarters and they comprise possibly the biggest myth that has ever pervaded thinking, teaching and practice in this field.

Professor Gordon pointed out the fallacies in these claims and the wholly unwarranted inferences which were being drawn from observations made on the dead. There was a failure to distinguish between clinical evidence derived from the living and the totally different order of things seen in the dead. In brief, he showed that asphyxia was not an entity which could be recognised from the post-mortem findings alone and, with the perspicacity of a Mendeleeff, he constructed what was virtually a periodic table for the classification of these deaths. On the basis of Gordon's observations, it become possible to pigeon-hole the various kinds of asphyxial death in categories which are acceptable scientifically and permit us to predict fairly confidently the abnormal signs which we can expect to find and which will give us an indication of how the chain of events leading to a fatal outcome was initiated.

Although Gordon's classification requires us to abandon the use of the scientifically inadequate term asphyxia (it means ``without a pulse'') and to substitute for it the more appropriate term anoxia (which means ``without oxygen''), this change in nomenclature has not yet been adopted universally, even though it is today used very widely (if in some cases still apologetically) in modern forensic writings. Our new generations of lawyers are becoming familiar with the acceptable scientific nomenclature, so it will not be long before the obsolete terminology is abandoned.

In the diagnosis of the so-called asphyxial deaths, our teachers set much store by the presence of small haemorrhages, pin-point to pin-head in size, on the surface of the lungs, the heart, and so on. These small haemorrhages are called petechiae (from the Latin for freckles). They have been likened to flea-bites. Indeed, their profusion in certain diseases of the kidney has led to the rather apt description of the flea-bitten kidney.

Notwithstanding the presence of petechiae in various disease processes unconnected with asphyxia, these small haemorrhages came to be regarded as diagnostic of mechanical obstruction to the airway. They acquired this asphyxial attribute largely as the result of the claims of the 19th Century physician, Tardieu. Despite some contemporary criticisms of Tardieu's assertions, the Tardieu spots (as they come to be known) were invested with a significance exclusively indicative of asphyxia. They became the hall-mark of the diagnosis.

Reliance on the Tardieu spots as evidence of asphyxia (indeed, of throttling) reached its misguided culmination in the case of Rex v Carr, first heard in the Port Elizabeth Circuit Local Division on 29 November 1948. In this case the Appellate Court set aside a conviction for murder and a sentence of death, after it had taken the unusual step of hearing new evidence. There were, of course, other issues besides the petechiae, but they were relied on by the chief witness for the Crown to support (on the evidence available) a wholly insupportable diagnosis of death due to throttling.

The Carr case stimulated Professor Gordon to initiate a most intense and fruitful programme of research in the field of forensic pathology. Careful studies on the petechiae revealed that they can occur spontaneously in the dead body and can even be produced as artefacts after death on the very surfaces of the organs where their presence has been regarded as indicating asphyxia.

It has, for example, long been observed that healthy infants have unexpectedly been found dead in bed or in their cots. In such cases we were taught that they had died from suffocation whether by smothering in thebedclothes or overlaying by parents. One of the signs relied on for calling them asphyxial deaths was the presence of Tardieu spots of petechiae on the surfaces of the lungs and the heart.

In the early 1960s it was realised that these deaths could not be explained in this way and the entity of unexpected death in infancy (or UDI, as I may call it) was recognised. We do not yet know why these apparently well infants die unexpectedly and suddenly, but the petechiae which are observed in these cases are no longer misinterpreted as evidence of mechanical obstruction to the airway. This is the direct result of Gordon's recognition of their non-specific character.

``... one thing is certain; they [the petechiae] cannot be accepted as indicating an `asphyxial' termination if by the use of the term `asphyxia' we infer mechanical obstruction to the entry of air into the alveoli. This was an erroneous view held by our forebears, and it has persisted longer than most other medico-legal myths. But it has now been discarded.''

The final touches to the work of Gordon in this area come with the demonstration that bruises in the tissues of the neck can be produced during the course of a post-mortem dissection and that it is not possible to distinguish, even microscopically, between such bruises and bruises inflicted recently before death. It is hardly necessary to point out that these observations have a profound significance for the post-mortem diagnosis of cases of throttling and other forms of violent death; nor is it surprising that they led to a modification of the technique of dissecting the neck structures that has been adopted widely.

It is fair to say today that the fundamental research work contributed by Professor Gordon and other South Africans has been adopted (if at times rather reluctantly, but adopted nevertheless), fairly generally in authoritative textbooks of international repute.

Thus the truth of the old tag of Pliny the Elder prevails: Ex Africa semper aliquidnovi.

A few words in conclusion

It is clear from what I have said that, once they entered the medico-legal theatre, South Africans did some major plastic and reconstructive surgery on the face of Forensic Pathology. This has forced medico-legal pathologists all over the world to take another, more informed look at the subject. They have not always shown alacrity in trying to overcome their resistance to the unsettling observations which our researches have forced them to adopt in place of outworn shibboleths. How could such things come out of the jungles of Africa? They did not apparently appreciate that a sophisticated medicine flourished in the best tradition of Western civilisation at the extremity of this vast continent.

This is why we have repeatedly, but politely, had to say to them, as Bernardo said to Horatio before Hamlet's approach:

``Sit down a while

And let us once again assail your ears,

That are so fortified against our story.''

Hamlet, Act I, Scene I.

If we approach our forensic problems in a scientific spirit, we will be able to say, with all the humility of the Soothsayer in Anthony and Cleopatra:

``In nature's infinite book of secrecy

A little I can read.''Act I, Scene II

Modest as this accomplishment may be, it is the only way in which we can advance the practice of our discipline so that we can play our proper part in the administration of justice.

Let us remind ourselves of what Sir Thomas Browne (1605±1682) said some 300 years ago in his treatise on Vulgar Errors:

``But the mortallest enemy unto knowledge, and that which hath done the greatest execution upon truth, hath been a peremptory adhesion unto authority; and more expecially, the establishing of our belief upon the dictates of antiquity ... . Now hereby methinks we manifestly delude ourselves, and widely walk out of the track of truth.''

Sir Thomas Browne, PseudodoxiaEpidemica; Enquiries into very many commonly received Tenents and commonly presumed Truths (1646).