Forensic Pathology Chapter 3 - The establishment of identity of human remains

The establishment of identity may be required upon…

intact fresh corpses - visual recognition, directly or by photography, may be made

hair color, 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 from the skeleton

direct measurement of body height, as well as serological investigations and organ abnormalities 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

Characteristics useful in identifying the dead - facial appearance

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 to have doubts about (or to even deny) the identity of the deceased person

hypostasis, contact flattening, edema, muscle flaccidity, and pallor (paleness) 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

Characteristics useful in identifying the dead - eye color

in the fresh corpse, eye color 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 color as a criterion of identity later than a few days following death

Characteristics useful in identifying the dead - skin pigmentation

in undamaged, unputrefied 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

Characteristics useful in identifying the dead - hair color

the head, pubic, and axillary hair is one of the most resistant identifying features, sometimes lasting millennia in favorable environments

the original color may, however, alter after burial, becoming a brownish-red or "foxy" color within as short a time as 3 months

the color may be obstructed by dirt or straining and expert treatment may be required to restore the original color

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 color conflicts with other positive evidence of identity

Characteristics useful in identifying the dead - hair structure

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

Cross-section of hair types

negroid hair - dark and having a spiral twist with a flattened, elliptical cross-section

mongoloid hair - less pigmented and is straight with a cylindrical cross-section

caucasian hair - round or ovoid cross-section but shows great variation in color and morphology (eyebrow hair tends to be triangular, pubic hair tends to be flattened)

Characteristics useful in identifying the dead - tattoos

deliberate ornamentation of the skin by introducing pigments under the epidermis has been practiced for millennia and in all parts of the world

many different pigments are used, as well as more unusual substances such as soot or gunpowder - the color is pricked into the upper dermis with a sharp instrument, once under the outer skin, the material persists for a long time

tattoos are the most helpful in identifying a body

Finger, palm, foot, and lip prints

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 do 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

Identifying scars

these can be important in the identification of unknown bodies, even when some degree of putrefaction exists

careful external examination may yield evidence that can assist in identification

Age of non-skeletonized bodies

the eyes are useful, in that a gray or white ring around the pupil (arcus senilis) is rarely seen below 60 years

up to the age of about 20-25, ossification centers and epiphyseal fusion are good indicators of age

Racial and ethnic characteristics

the deep pigmentation of a West African

the epicanthic folds of the Mongoloid races

the red-haired Celt

the pale blonde common is Scandinavia

clothing, ornaments, and other associated objects (it must be born in mind that other races may adopt these through choice, marriage, or deception)

hair texture, style, and length and beards

physical artifacts include penile and vulval circumcision, nose and ear piercing, lip perforation, tribal facial scars, and earlobe distension

Samples required for DNA testing

postmortem material is inferior to live blood and tissue for DNA profiling if any significant postmortem change has proceeded enough to break down nuclear chromatin

plain blood samples should be taken, however, though leukocytes may have already disintegrated

the best material is said to be muscle or spleen and, if decomposition is advancing, the bone marrow is recommended

at least 0.5 g of tissue should be cut from the parenchyma of an organ and placed in a small plastic tube with no fixative or preservative - this should be frozen at -20 degrees C if there is likely to be the slightest delay in transmission to the laboratory

in sexual offenses associated with homicide, as much material as can be obtained from the vagina should be collected - either by pipette or multiple swabs from vagina, rectum, and mouth

The general categorization of skeletal remains

when objects though to be skeletal remains are found, the following questions need to be asked, and, where possible answered - are they bones, are they human bones, what is the sex, what is the stature, what is the race, what is the age, how long have they been dead and/or concealed, and what was the cause of death

Are the remains actually bones?

recognition is usually easy, but the shape, texture, and especially weight of the objects

greater difficulty may be experienced when stimulated human "bones" are found - the abnormal lightness would indicate the true nature

Are the bones of human origin?

first, the size is assessed and many small, slender bones excluded on obvious grounds

when bones are incomplete or fragmentary, the problems escalate rapidly - if the ends of longer bones are present, then their non-human shape may be more readily determined, but cylindrical segments of the central shaft have little in the way of distinguishing features, apart from size

burnt bone fragments offer similar problems, added to which is the possibility of heat distortion and shrinkage

histological examination may offer a species differentiation or at lest to exclude a human origin

if the bones are too fragmentary to provide any anatomical data, then serological investigations must be attempted - these depend on species-specific proteins being extracted from the bone into solution where they can be test against specific antisera thus the test is essentially seeking plasma constituents within the bone, the recognition being carried out but techniques such as electrophoresis or gel diffusion

DNA can now identify human tissue, if not the alternative species

The determination of sex

the accuracy of determination of the sex of skeletal remains varies with the age of the subject, the degree of fragmentation of the bones, and biological variability

the determination of sex is statistically the most important criterion, as it immediately excludes approximately half the population whereas age, stature, and race each provide points within a wide range of variables

obviously sex differences do not become apparent until after puberty, usually in the 15-18 year period (never say the sex of skeletons on young kids)

Main difference in pelvis bones in males and females

the main differences between males and females in the pelvis are due to females biological ability to bear children

the most reliable method is the Phenice method, which uses 3 areas and the presence and absence of certain characteristics

Is this person male or female?

sexual differences in the human skeleton begin before birth although they are not truly diagnostic until after puberty

in general, females' post cranial skeleton develops faster than males and this difference in rate can be used to infer sex in prepubertal individuals

typically, however, sex should not be estimated unless the individual is of an age when puberty has begun; above 18 years of age, sex can be determined with confidence

the two areas that are used most often to determine the sex of an individual in life are also the most diagnostic in death - the pelvis and skull

other bones can be very useful for estimating sex as well, and with only a few measurements, an experienced anthropologist can be accurate 70-90% of the time

Gender identification - pelvis (pubic body)

female - has a wider pubic body

male - has a more narrow pubic body

Gender identification - pelvis (subpubic angle/subpubic concavity)

female - has a wider subpubic angle (greater than 90 degrees)

male - has a more narrow subpubic angle (less than 90 degrees)

subpubic angles on a skeleton is the most helpful when determining the sex of a skeleton

when the angle is too narrow during pregnancy, a c-section is required to deliver the baby

Gender identification - pelvis (pelvic inlet and sacrum)

female - the pelvic inlet is round, the sacrum is shorter and wider

male - the pelvic is "heart-shaped", the sacrum is longer and more narrow

Gender identification - pelvis (greater sciatic notch)

female - the sciatic notch is wide (about 60 degrees)

males - the sciatic notch is narrow (about 30 degrees)

Gender identification - pelvis (ventral arc)

females - ventral arc is characterized by a slightly raised ridge

males - do not exhibit the ventral arc

Gender identification - skull (forehead)

female - rounded forehead

male - sloping, less rounded forehead

Gender identification - skull (eye sockets)

female - round eye sockets

male - squarer eye sockets 

Gender identification - skull (mandible angle)

female - sloping (obtuse) angle of the jaw

male - vertical (acute) angle of the jaw (closer to 90 degrees)

Gender identification - skull (skull size)

female - smaller and lighter skull

male - larger and heavier skull

Gender identification - skull (brow ridge)

female - smooth brow ridge

male - prominent brow ridge

Gender identification - skull (chin shape)

female - pointed chin

male - square chin

Gender identification - skull (mastoid and zygotic process)

female - less defined mastoid process, and zygotic process ends before the auditory meatus

male - more defined mastoid process, zygotic process extends well behind the auditory meatus

What connects muscle to bone?

Tendons connect muscle to bone, stays longer on the skeleton for longer during decomposition (the last one to decompose)

males have more pronounced muscle attachment

Gender identification - femur

determination of sex of femur by angulation of the shaft - the condyles are set on a flat surface and the angle of the shaft is measured

female - because of the greater tilt caused by the wider pelvis, the female angle is usually less than 80 degrees

male - greater than 80 degrees

Evidence of pregnancy from the skeleton

more accurately, parturition causes some changes in the pelvis as a result of the local trauma of childbirth, which is reinforced by multiple pregnancies

these include "pubic scars" from the tearing of tendon insertions and periosteum around the pubic bone

the dorsal pubic surface and the pre-auricular sulcus are best indicators, but most authorities agree that it is not possible to determine the number of births from osteological appearances

Estimation of stature from skeletal remains

this is more difficult than any of the preceding investigations, partly because racial traits are not so marked and partly because so much ethnic mixing has taken place, especially in the large-scale immigrations into Europe and North America

there are 3 main racial groups - Caucasian, Mongoloid, and Negroid

the skull offers the best evidence on racial origins

one of the most useful pointers to a Mongoloid skull is the presence of posteriorly concave, "shovel-shaped" upper incisors

How to estimate the height of an individual using a skeleton

when measuring height estimation, a long bone (usually femur) is preferred

Personal identity from skeletal material

anatomical shapes that can be matched by radiology, measurement or other means

discrete abnormalities such has healing fractures, metal prostheses, bone disease, or congenital defects

Frontal sinus identification

it is particularly useful in mutilated or burnt bodies - the sinuses are well protected from all but the most extreme damage and are unique

no two persons (not even identical twins) have the same profile of these air spaces

they appear in the second year of life and increase in size for the first 2 decades

they are absent in about 5% of persons and unilateral in another 1%

for the sinuses to be used, an ante-mortem anteroposterior skull radiograph must be available, the most common source being from a previous hospital admission or examination

The dating of skeletal remains - physical appearance

recent bones will have soft tissue remnants adhering, in the form of tendon and ligament tags (especially around joint ends)

periosteum may be visible as fibrous material closely adherent to the shaft surface 

cartilage may also be present on articular surfaces 

Physical tests

fluorescence in ultraviolet light can be a useful preliminary test

DNA

people have dealt with cases where DNA testing was successful after a few years' burial, but other more recent skeletons did not yield such success

however, far older archaeological material has given DNA profiles, so, at present, the DNA criteria cannot be used for dating

Photo-superimposition techniques for identification

where potential candidates for the identity of a skull are known to the investigating authority and photographs taken during life are available, a well-established technique used for identification is photo-superimposition

in this method, photographs of the skull are taken in exactly the same orientation in three planes as the available photograph

these are then enlarged to exactly the same dimensions as the photograph, an either the negative or a positive print is made on transparent film

Reconstruction of the facial appearance from the skull - modeling clay

the method depends on a pre-knowledge of the usual tissue thickness at a multitude of points on the normal skull, an anatomical expertise that now has quite a large database

modeling clay is laid on to the unknown skull in layers corresponding to these standard thicknesses, then more imaginative modeling added to humanize the basic shape

the obvious defects in this technique are the lack of knowledge about eyes, lips, nose, ears, and head hair, all of which contribute greatly to individual characteristics

Reconstruction of the facial appearance from the skull - digital

more recently, a combination of video and laser equipment has allowed 20,000 measurements to be taken and stored within 30 seconds

the data from an unknown skull are then electronically modified on screen to produce various images