Under the Microscope: The identity

 

The identity of the dead is an essential part of post-mortem examination, for various reasons. These include:

-          the ethical and humanitarian need to know which individual has died, especially for the information of surviving relatives;

-          to establish the fact of death in respect of that individual, for official, statistical and legal purposes;

-          to record the identity for administrative and ceremonial purposes in respect of burial or cremation;

-          to discharge legal claims and obligations in relation to property, estate and debts;

-          to prove claims for life insurance contracts, survivor's pensions, and other financial matters;

-          to allow legal investigations, inquests and other tribunals, such as those held by coroners, procurators fiscal, medical examiners, judges and accident enquiries to proceed with a firm knowledge of the identity of the decedent;

-          to facilitate police enquiries into overtly criminal or suspicious deaths, as the identity of the deceased person is a vital factor in initiating investigations;

The establishment of identity has many facets, some of which have no medical content, such as the recognition of clothing, documents and personal property. Some aspects, though primarily the responsibility of the police, have a medical content, including identification of fingerprints and personal property such as hearing aids, spectacles, medicines, trusses and surgical prostheses. False dentures, have such central importance that they will be considered in the section on odontology. The establishment of identity may be required upon:

-          Intact fresh corpses. Here visual recognition, directly or by photography, may be made. Hair colour, skin pigmentation, scars and tattoos can be examined without difficulty;

-          Decomposed corpses. Many surface features may be partially or wholly lost, but more information can be obtained than from a skeleton. Direct measurement of body height, for example, may be possible, as well as serological investigations and organ abnormalities, such as past surgical intervention, may be found.

-          Mutilated and dismembered corpses. Depending on the degree of mutilation and the amount of tissue missing, identification may be hampered. If the remains are fresh, facts such as racial pigmentation may be determined, but direct measurement of stature may be impossible. Selective mutilation in some homicides may be deliberately directed at frustrating identification, such as the removal of teeth and finger-pads.

-          Skeletonized material. If all soft tissues are absent, identity depends solely on osteological examination and measurements and the recognition of any pathological or anatomical abnormalities in bone.

Even in perfectly fresh bodies, recognition may be difficult  because of alterations in the features caused by death. It is a common occurrence in mortuary viewing rooms for a close relative, even a parent or spouse, to have doubts about - or even to deny or mistakenly agree to - the identity of the deceased person. Though distress and emotion play a part, changes in the features may be profound. Hypostasis, contact flattening, oedema, muscle flaccidity and pallor may all combine to distort the face. Recognition in the living is partly a dynamic process, aided by facial muscle tone and especially eye contact and movement, all of which are absent in the corpse.

 

In the fresh corpse, eye colour corresponds with the living state, but it quickly deteriorates. Loss  of intraocular tension and clouding of the cornea develops progressively within a few hours, making the iris harder to observe. Collapse of the front of the globe occurs within a day or two and, with developing decomposition, all irises tend to 'darken to brown. It is unsafe to depend on eye colour as a criterion of identity later than a few days following death - or even much sooner where environmental conditions hasten decomposition.

In undamaged, unpetrified bodies, the major ethnic differences in skin pigmentation are obvious, though the slight melanin increase of the misnamed 'yellow' races of Asia may be impossible to differentiate from Mediterranean or Middle Eastern races. The onset of deathly pallor and postmortem hypostasis is more profound than slight variations between sunburnt White people, northern Asians or Semitic races. When putrefaction sets in, skin slippage progressively removes the pigmented layers and eventually pigmentation becomes unavailable as a marker of identity, though histologically melanin may still be visible in the basal layer of any surviving epidermis. Burnt bodies may also lose pigmented skin, either by heat destruction or by deposition of soot and other combustion products on the surface, though it is rare for this to be so complete as to obscure all evidence of pigmentation.

The head, pubic and axillary hair is one of the most resistant identifying features, sometimes lasting millennia in favourable environments. The original colour may, however, alter after burial, becoming a brownish-red or 'foxy' colour within as short a time as 3 months. The colour may be obscured by dirt or staining and expert treatment (usually by a biologist or museum technologist) may be required to restore the original colour. The possibility of deliberate chemical coloration or bleaching before death may have to be considered and again expert chemical analysis in a forensic science laboratory may be needed to confirm or eliminate this if the hair colour conflicts with other positive evidence of identity.

This is more the province of the forensic biologist or  anthropologist, but factors such as whether the hair ends - - have been cut or are naturally pointed may sometimes have importance in identity. Racial features exist, Negroid head hair being dark and having a spiral twist with a flattened, elliptical cross-section. Mongoloid hair is less pigmented and is straight with a cylindrical cross-section. Caucasian hair is round or ovoid in cross-section, but shows great variation in colour and morphology compared with the other two major ethnic groups. Though head hair in Caucasians is round to ovoid in section, eyebrow hair tends to be triangular and pubic hair flattened. Where a hair root is present, blood grouping and other serological criteria can be determined. Grouping of the shafts of hairs has been repeatedly attempted and success claimed by some workers. The cells of the hair root can give a DNA profile and mitochondrial DNA (mtDNA) has been detected even in a sample from a single hair shaft. Microscopic examination of the hair can assist in determining the species, if not human.

Deliberate ornamentation of the skin by introducing pigments under the epidermis has been practised for millennia and in all parts of the world. The word 'tattoo' comes from the Polynesian 'ta tau', meaning 'to mark'. Some races such as the Ibans of Sarawak may be tattooed over much of their body surface, but many men and some women in most countries have localized tattoos, which can be of considerable assistance in identification. Many different pigments are used, as well as more unusual substances such as soot or gunpowder. The colour is pricked into the upper dermis with a sharp instrument, usually a needle used manually, or by an electric vibrator. Once under the outer skin, the material persists for a long time. Colours such as blue, green or red may be scavenged by tissue cells and leached into the lymphatic system after a number of years or decades. Black pigments, usually carbon particles in the form of Indian ink, are so resistant as to be virtually lifelong, though some may be transported to regional lymph nodes. Thus an original pattern of different colours may fade differentially over years, the black areas standing out in strong relief. The patterns are so diverse as to defy classification, though much has been written on the subject. From the point of view of identity, tattoos may be useful in both a general sense and for comparison with potential victims. The general applications require a knowledge of ethnic, national, cultural, religious and social practices, so that the tattoo can be assigned to some particular group of people. In Western society, the popularity of tattooing changes from time to time. Former statements that tattoos are seen mostly in the 'lower social classes' have little current validity, though it is obvious that bankers and parsons are less likely to sport tattoos than seamen and truck drivers.

Tattoos are of most use when individual enough to be  compared with known designs on a missing person. The design is often supplemented by actual names, though these are mostly forenames rather than family names. Designs are by no means unique and a professional tattooist may turn out hundreds of identical decorations, so names are a bonus when trying to achieve identity. Initials may be used, but these can be misleading due to the use of nicknames and diminutives, such as 'B' for Bill, rather than William. In general, men have the names of girls on their tattoos, but initials are usually their own. Conversely, women with tattoos almost always display the names of sweethearts, rather than their own. Some tattoos may be numbers or unadorned names, the most tragic examples being those from Nazi concentration camps during the last war.

The photography, distribution and matching of tattoos is police business, but the pathologist's duty is to make them accessible and clear to the police. Where decomposition has set in,  tattoos may be obscured by wrinkled, peeling epidermis, but often this can be wiped off to reveal tattoos that are more vivid than on fresh skin. Once the tissues become green and slimy then the pattern progressively vanishes, but early decomposition is no barrier to recognition. Where skin pigmentation may hide a design, skin slippage may actually enhance the clarity, especially of the weaker colours like blue, red and green. Attempts at the deliberate removal of tattoos are common, either from regret at having disfigured the body during youthful or drunken euphoria, or to remove evidence of identity. Many methods have been used, from surgical excision to scarification with sandpaper and from caustic soda to electrolysis. All methods depend upon damage to the epidermis and dermis, with consequent inflammation and scar formation. The tattoo can certainly be removed, but always by replacing it by a cicatrix to a greater or lesser extent, which will itself indicate that something pre-existed at that site.

The science of fingerprints, their classification, retrieval from records and methods of recording lie in the domain of police procedure, and, as with tattoos, the pathologist's role is merely to facilitate the taking of prints by police officers. Sometimes, when a strange print is found at a scene of crime, the police may wish to take the fingerprints of doctors who visited the locus to eliminate them from their enquiries and there is obviously nothing objectionable about this. Indeed, some forensic pathologists who habitually assist the police leave their prints on file so that they are permanently available for exclusion. When called to a scene of death, the doctor should take care to avoid handling objects and furniture to reduce the need for such laborious screening of prints. The doctor need know nothing about fingerprints except for his own interest, though it is as well to be prepared for the inevitable questions - no two fingerprints have ever been found to be identical and even identical twins have different prints. However, some recent claims point out that some prints are so similar that the criteria usually accepted as proof of congruence may not be sufficient. Police usually attend the mortuary to take full sets of fingerprints in the usual way by rolling ink on to the finger-pads and pressing the pulps against record cards. The pathologist may help when there is strong rigor present, by either forcing the flexed fingers back or even by slitting the flexor tendons, though this has the danger of fouling the fingers with blood.

When the body is putrefied, the doctor can again assist by removing desquamated casts from the fingers for the police. These may need to be preserved or hardened up so that the decaying tissue does not lose further definition from the ridges that form the prints. The skin may be placed in formalin, alcohol or glycerine solution, especially where maceration in an immersed body has caused swelling and blurring of the epidermis. An alternative is immersion in 20 per cent aqueous acetic acid for 2-8 hours. Rarely, a criminal may attempt to obliterate his fingerprints by scarring the finger pads. To be effective, this must be drastic enough to damage the underlying dermis and the consequent cicatrices will be more obvious than the original prints. Surgical grafting of skin from elsewhere on the body has been reported as a means of removing fingerprints, but again the result is self-evident proof of nefarious intent.

 

Scars on the skin may arise from any previous injury that has breached the epidermis, as superficial injuries to the upper layer of skin will heal without a trace. Where the dermis has been entered, healing occurs by organization of the plug of blood clot and/or granulation tissue. If the wound is narrow, such as that inflicted by a surgical instrument, sharp knife, razor or glass, then if the edges are kept together, especially by stitches or dressings, the resulting scar will be narrow and insignificant. Gaping or infection will widen the scar and obviously larger lacerations or burns will result in similarly greater scarring. In relation to identification, scars are of use only if those thought to be the victims are known to have similar scars, both in nature and position. The specificity of scars varies greatly, as many people may have appendicectomy scars, and many women have had hysterectomies or other gynaecological operations that leave lower abdominal scars.

Turning to traumatic scars other than surgical, the pathologist may be able to recognize the cause, which can assist in identity. Naturally the vast majority of non-surgical scars are the result of accidental trauma and where family, friends, photographs or medical records indicate the existence of specific scarred sites on the body, then confirmation of identity may be greatly assisted or confirmed. Some scars are deliberately produced as part of some ethnic or religious tradition, such as the facial scars, in some African tribes, as well as deformed or perforated ear lobes or lips.

The age of a scar is very difficult to assess and, once it becomes mature, no change will occur for the rest of the person's life. When a linear wound is inflicted, be it a surgical operation or a knife slash, the edges become mechanically strong within a week, assuming that no infection or haematoma develops. The wound is brownish red at this stage and remains vascular for several months, depending upon its width. The pinkness of contained blood vessels gradually fades and a narrow surgical incision may be white by 4-6 months. The avascular collagen tends to shrink for a year or so, but is white-silver after a year and remains in this state indefinitely.

Histology does not contribute much to the examination of scars, except to confirm that a skin mark actually is a scar. Stains for collagen or elastin may confirm the discontinuity in the dermis. Scars do not carry hair follicles, sweat glands or sebaceous glands, though an occasional accessory skin structure may be present as a result of the inclusion of a viable fragment of original skin in an irregular wound - or where surgical repair has detached or invaginated a piece of the margin.

 

 

Acknowledgements:

www.politie.nl  Politiekorpschef  @Janny Knol©

www.aived.nl    AIVD – @Erik Akerboom ©

www.politie.nl WEB Politie - @Henk van Essen©

https://www.police-nationale.interieur.gouv.fr/ @ Stephane Folcher ©

 

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