Bruises

A bruise is a haemorrhage into tissues. Synonyms are
contusion and ecchymosis (plural: ecchymoses). Very small
bruises, ranging in size from a pinpoint to a pinhead, may be
described as petechiae, or petechial haemorrhages, or
alternatively as punctate haemorrhages. Haemorrhage or
bleeding is the process which produces a bruise in tissues, but
the term haemorrhage also encompasses bleeding which may
not be associated with bruising, e.g. a bleeding nose, or a
bleeding stomach ulcer.

Any tissue may bruise, but bruises confined to deeper tissues,
such as skeletal muscle, are not visible on the skin surface.
Bruises of the deep tissues, even when fatal, may not be
evidenced by any injury to the skin surface. For example, a
fatal head injury, such as a sub-dural haemotoma, may be
encountered without recognisable superficial bruising; fatal
strangulation with extensive bruising of the muscles of the
neck may be accomplished without obvious bruising of the
skin; and blows to the abdomen, although producing bruising
and ruptures of internal organs, may not produce any
abdominal wall bruising.

Only bruising of the skin and subcutaneous tissues, and the
mucosa of the mouth, vagina and anus, is visible at a clinical
examination. A simple bruise is a discolouration resulting
from haemorrhage beneath the skin or mucosa, without any
associated breach in the surface. The blood vessels ruptured
are typically the capillaries and small veins rather than
arteries. Skin and mucosal bruises may be accompanied by
abrasions and lacerations, but they are not usually associated
with cuts and stabs, where there is a free flow of blood from
the cut vessels rather than infiltration of blood into the tissues.
Bruises are accompanied by swelling from the haemorrhage
itself and the resulting inflammation. If the extravasated blood
collects as a discreet tumour-like pool, the lesion is referred to
as a haematoma. Bruises are usually painful and tender to
palpation as a result of damage to local nerve endings and the
inflammation. Focal necrosis of subcutaneous fat may occur at
the site of a bruise, and a secondary aseptic inflammation in
response to the irritant effect of fat liberated from the ruptured
cells produces a hard chronic lesion. This is more of clinical
than forensic importance since a common site is the breast
where it may be mistaken for a carcinoma. Bruises of the skin
if numerous and large enough can be life-threatening as a
result of blood loss but this is an uncommon occurrence.
Bruises are produced typically by a blunt force impact, such as
a blow or a fall, but can result also from crushing, squeezing
or pinching. Bruising, with or without abrasion, to the bony prominences
of the back (i.e. the shoulder blades, sacrum and
pelvis) may be caused by force applied to the front of a supine
body with resultant counter-pressure between an underlying
firm surface and the back, as in forceful restraint on the
ground during a rape, or a stamping assault. Similar ‘counterpressure
bruising’ may be seen on the bony prominences of
the front of the pelvis (the anterior superior iliac crests) in
attempted anal rape. So called ‘love-bites’ (‘hickeys’ in
American slang) are superficial bruises produced by the
negative pressure of mouth suction. They are commonly found
on the side of the neck and occasionally the breast and inner
thigh. They are sometimes self-inflicted on accessible parts of
the arms to simulate evidence of an assault. Natural diseases in
which there is an abnormality of the clotting mechanism of the
blood, such as leukaemia, scurvy (vitamin C deficiency), and
liver disease, cause so-called ‘spontaneous bruising’ which is
thought to result from unrecalled trivial trauma. Florid
spontaneous bruising (purpura) may be seen in children with
fulminating meningococcal infection.

The size of a bruise is an unreliable indicator of the degree of
force which caused it, because several other factors, such as
anatomical site, gender, age and the presence of natural
disease, all influence bruise size. Bruising occurs more
readily where there is a lot of subcutaneous fat, such as on the
buttocks and thighs, and therefore more readily in the obese, in
women and in infants. Bruising occurs readily in loose
tissues, such as around the eyes and genitals, and less readily
where the skin is strongly supported by fibrous tissue, such as
the palms, soles and scalp. The elderly bruise more easily
because of degenerative changes in the blood vessels and the
supportive tissues of the skin and subcutaneous fat. Senile
purpura, characterised by sharply-defined geographic areas of
‘spontaneous’ bruising to the backs of the hands and forearms
is found in the very old or frail. Natural diseases which affect
blood clotting, degenerative diseases of small blood vessels,
and high blood pressure make some individuals more
susceptible to bruising. Skin colour does not change the
extent of bruising but does significantly influence its
appearance because the bruise is viewed through the semitranslucent
skin. Bruising is most easily seen in very paleskinned
individuals, particularly blondes and redheads, and
can be completely masked by the natural skin colour of blacks.
Examination under ultraviolet light helps reveal bruises which
are otherwise difficult to see. Black and white photography,
which is more sensitive to ultraviolet light than colour
photography, may allow the bruise to stand out more clearly in
a photograph.

Bruises tend not to reflect accurately the shape of the object
which produced them, and they change shape with time.
Exceptionally the surface detail of the striking object may be
imprinted as a patterned bruise on the skin, often associated
with a patterned abrasion. Such patterned or imprint bruises
typically occur following a heavy impact, such as from a shod
foot or motor vehicle, or from the muzzle or foresight of a gun
in a contact gunshot wound, with death occurring soon after
injury, and so limiting the diffusion of blood and the obscuring
of the imprinted pattern. Patterned bruises commonly have a
bright red intra-dermal component whose diffusion is limited
also by the dense collagenous dermal tissue. Occasionally clothing
or jewellery may leave a patterned bruise on a body
when it is crushed into the skin surface by an impacting object,
e.g. a motor vehicle striking a pedestrian, or a kick through
clothing.

Sometimes bruises give a more general impression of the
causative object, for example a doughnut-shaped bruise is
produced by a hard object with a rounded contour, such as a
cricket ball or a baseball. A similar mechanism produces two
parallel linear bruises, so-called ‘tram-line’ or ‘rail-track’
bruises, as the result of a blow from a long object which has a
circular cross-sectional shape, such as a police baton, or an
electric flex. If the flex has been looped then this may be
apparent as curved rail-track bruising. When a blow with a rod
is struck against the buttocks, - a particularly pliable, curved,
soft surface - the tissues are compressed and flattened under
the impact and the resulting rail-track bruise will follow the
curved contour of the buttocks. A pliable weapon such as a
strap or electric flex may produce a similar appearance
because it can wrap around the body on impact. Bruises
produced by finger-pads as a result of gripping are usually
larger than the finger-pads themselves, but their number,
pattern and location on the victim suggests the mechanism of
causation. Finger-pad bruising is seen on the neck in
throttling, on the upper arms in restraint, on the thighs in rape,
and on the chest and face in child abuse.
Bruises change colour as they age before finally fading away.
A fresh bruise is dark red, the colour of venous blood, turning
soon to a dusky purple. Thereafter the colour changes
progressively from the periphery of the bruise towards the
centre through brown, green, yellow and a pale straw colour
before disappearing. These
colour changes reflect the breakdown of haemoglobin into
coloured products as part of the inflammatory process. The
time frame of the colour change is extremely variable
depending upon bruise size, depth, location and the general
health of the individual, but most bruises disappear within one
to four weeks. ‘Love bites’, which are small and superficial,
typically complete this sequence in seven days.

In general, bruises which have a green or yellow margin are
three or more days old and those which appear entirely dark
red or dusky purple are fresh having occurred within a day or
so. The accurate estimation of the age of a single bruise is not
possible but fresh bruises are easily distinguished from bruises
several days old. Establishing that bruises are of different
ages, and therefore inflicted at different times, is important in
the assessment of allegations of repeated assaults, such as in
child abuse and spousal abuse. Chronic alcoholics commonly
have multiple bruises of different ages over their legs and arms
as a result of repeated falls when drunk, often with the extent
of bruising made worse by disturbances of blood clotting
secondary to alcoholic liver disease.

The colour of bruises does not change after death, but they
may become more evident against the now pale skin, or
alternatively be obscured by the post-mortem skin colour
changes of lividity and decomposition. It is not possible to
distinguish a bruise sustained at the time of death from one
which occurred up to a few hours earlier, and such bruises are
best described as having occurred ‘at or about the time of
death’. If the microscopic examination of a bruise shows an
inflammatory reaction then it was likely inflicted more than a
few hours before death, and almost certainly more than half an
hour before.

Bruises to the deep tissues can be present without any evident
skin surface injury, particularly if the force applied is by a
smooth object over a wide area. Such deep bruises may
spread under the influence of gravity and body movement,
following the path of least resistance along natural or
traumatic planes of cleavage of the tissues. This shifting of deep
bruises explains their delayed appearance at the skin
surface some days after infliction, often at sites distant from
the points of impact. The delayed appearance of bruising
around the eyes follows a blow to the forehead, bruising
behind the knee follows a blow to the lateral thigh or a
fractured neck of femur, and bruising to the neck follows a
fractured jaw. A second examination of a victim of an assault
after an interval of a few days may show visible bruising
where previously there had been only the swelling or
tenderness of deep bruising. Such second examinations are
recommended as best practice.

Bruising is essentially a vital phenomenon in which the
infiltration of blood into the tissues occurs under the pressure
of the circulating blood. After death, the lack of blood pressure
means that it requires considerable force to produce a bruise in
a corpse. Such post mortem bruises are disproportionately
small relative to the force applied, which may be evident from
associated fractures, and the resultant bruises are usually only
a few centimetres in diameter. In assessing the possibility that
bruising may be post mortem, the findings and circumstances
as a whole should be considered, and against this background
quantitative differences between ante mortem and post
mortem bruises are usually so great that confusion is unlikely.
It is seldom difficult to distinguish between injuries with vital
bruising resulting from a vehicle running over a live body, and
the tearing and crushing of dead tissues. However, finger-pad
bruises to the insides of the upper arms may be produced by
simply lifting a corpse, particularly in those elderly women
who have abundant loose upper-arm fat, which is often
congested due to post mortem lividity. Any livid dependent
areas of a corpse bruise more readily post-mortem as a result
of the vascular congestion.

Post-mortem lividity, which is gravitational pooling of blood
within the blood vessels after death, may be confused with
bruising. However, the pattern and distribution of lividity
usually makes the distinction straightforward. In doubtful
cases, incision of the skin discloses blood oozing from the cut
ends of vessels and washing the cut surface removes the
blood, whereas the blood infiltrating the tissues in bruises
cannot be washed away. If needed the distinction may be
confirmed by microscopic examination. In a fair-skinned
corpse the congested muscles of the base of the thumb (thenar
eminence) and dorsum of the foot may be visible through the
thin overlying skin and superficially resemble bruising. Post
mortem decomposition with its initial green discolouration of
the anterior abdominal wall is readily distinguished from
bruising by its colour and location. Putrefactive haemolysis of
blood within blood vessels and decompositional breakdown of
vessel walls results in extravasation and diffusion of
haemolysed blood into adjacent tissues, and this haemolytic
staining of tissue may entirely mask small ante mortem
bruises, e.g. in the neck muscles in cases of throttling.