Q2 LONG ANSWER 10M ★ High-yield

Describe abrasions and contusions with their types, ageing and medicolegal importance.

Forensic Medicine · 2nd Professional — Para-Clinical

Abrasions

An abrasion is an injury involving the superficial layers of the skin (the epidermis), caused by friction against a rough surface or by a tangential or perpendicular blunt force. It heals without a scar unless the dermis is involved.

Type	Description and value
Scratch (linear abrasion)	Caused by a sharp-pointed object drawn across the skin — a pin, thorn, or fingernail. The direction is shown by epidermal tags heaped at the far (terminal) end
Graze (sliding, brush burn, gravel rash)	The commonest type, from a broad tangential impact — a fall on a road or being dragged. Shows parallel linear parchment-like streaks; the direction is again given by the heaped epidermis at the terminal end. Characteristic of road traffic accidents
Pressure (crushing) abrasion	From perpendicular pressure crushing the epidermis — the ligature mark in hanging and strangulation, and a bite mark
Imprint (patterned) abrasion	The most valuable type, because it reproduces the pattern of the object — a tyre tread, the radiator grille of a vehicle, a woven fabric, the muzzle of a firearm, or the teeth of a comb. It may identify the weapon or vehicle

Nail marks are of particular importance: curved or crescentic abrasions on the neck in throttling, on the face in smothering, on the inner thighs and breasts in sexual assault, and on the wrists and arms from gripping. The concavity faces the direction from which the pressure came, so their orientation indicates the position of the assailant
Age of an abrasion — fresh: bright red and oozing serum or blood; 12 to 24 hours: a bright reddish scab forms; 2 to 3 days: the scab is reddish-brown; 4 to 7 days: dark brown to blackish, and the scab begins to loosen at the periphery; after about 7 days: the scab falls off leaving a depigmented area which gradually assumes normal colour. These timings are approximate and are affected by the site, size, depth and infection
Medicolegal importance — it marks the site of impact, which is its greatest value since it is always at the point of contact; it may indicate the nature of the surface or weapon; the direction of the force; the manner of the assault (nail marks, ligature mark); and the age of the injury. It is also important because a trivial-looking abrasion may overlie a fatal internal injury
A postmortem abrasion is yellowish, translucent and parchment-like, with no vital reaction and no bleeding — commonly produced by dragging the body or by ant activity

Contusions

A contusion (bruise) is an extravasation of blood into the tissues, produced by the rupture of small vessels by a blunt force, with the overlying skin remaining intact.

Colour	Approximate age	Basis
Red	Immediate, first few hours	Extravasated oxygenated haemoglobin
Blue / bluish-black	Few hours to 3 days	Deoxygenation of haemoglobin
Green	4 to 5 days	Biliverdin
Yellow	7 to 10 days	Bilirubin
Normal colour	14 to 15 days	Haemosiderin removed by macrophages

The colour change proceeds from the periphery toward the centre, since breakdown begins at the margins where the macrophages act first; so a bruise may show several colours at once and the outermost is the oldest
The timings are unreliable and must be given as a wide range. The only reasonably firm statement is that a yellow bruise is more than about 18 hours old; beyond that, individual variation, depth, site and the size of the bruise make precise dating indefensible. Studies have shown experienced examiners dating bruises wrongly from colour alone, and this must be acknowledged in evidence

Factor	Effect on bruising
Age	Children and the elderly bruise easily — loose delicate tissue and fragile vessels; the elderly also show senile purpura on the forearms and hands from trivial contact
Sex and build	Women and obese persons bruise more readily — more subcutaneous fat and delicate skin
Site	Lax, vascular tissue bruises readily — the eyelids, scrotum and lips; tissue over bone bruises readily on a small force; areas over dense tissue such as the palm, sole, scalp and abdominal wall bruise poorly, and a severe blow there may leave NO external bruise at all
Disease	Haemophilia, thrombocytopenic purpura, scurvy, leukaemia, liver disease, and anticoagulant therapy — producing spontaneous or grossly disproportionate bruising, which must be excluded before alleging assault
Skin colour	Bruises are harder to see in dark skin; good lighting, and where necessary incision or infrared photography, are needed
Force and weapon	Greater force gives a larger bruise, but the relationship is not proportional and no estimate of force should be attempted

CLINICAL PEARL

The size of a bruise does not measure the force, and its position may not mark the blow. Blood tracks along fascial planes under gravity, so a bruise may appear at a site distant from the impact — a blow to the forehead producing a "black eye", or a fractured pelvis producing bruising in the scrotum. And a severe blow to the abdomen or the back may rupture the liver with no visible bruise whatever. Neither the presence nor the absence of a bruise is a reliable index of what happened.

Patterned and Artificial Bruises

Tramline (railway line) bruising — two parallel linear bruises with a pale central zone, produced by a blow with a rod, stick, cane or belt. The blood is displaced from directly beneath the rod to either side, which is why the centre is spared. It indicates the width of the weapon and is strong evidence of beating
"six-penny" (fingertip) bruises — small round or oval bruises in groups of three or four, from gripping fingers; on the upper arms, wrists, thighs and neck; indicating restraint or throttling
Other patterns — the imprint of a shoe, a buckle, a bite, a ligature, or the weave of clothing crushed against the skin
Artificial (fabricated) bruises — produced by applying the juice of irritant plants, most notoriously the marking nut (Semecarpus anacardium, "bhilawa") in India, and Calotropis, Plumbago and croton oil. The marking nut produces irregular, tongue-shaped or linear lesions with vesicles, itching and burning, sited on accessible parts, and characteristically discoloured black-brown with an irregular outline that does not correspond to any weapon. The juice can be recovered from the lesion and identified chemically, and the lesions are itchy, which a genuine bruise is not

Abrasion and Contusion Compared

Feature	Abrasion	Contusion
Tissue involved	Epidermis (superficial layers of skin)	Subcutaneous and deeper tissue; skin intact
Mechanism	Friction against a rough surface	Blunt impact rupturing small vessels
Relation to the site of impact	Always at the exact site of contact — its greatest value	May be distant, since blood tracks along fascial planes under gravity — a forehead blow giving a black eye
Appears immediately?	Yes	May be delayed by hours or a day, particularly if deep
Indicates the weapon?	Often — an imprint abrasion reproduces the pattern	Sometimes — tramline bruising indicates a rod and its width
Ageing	By the colour and adherence of the scab	By colour change — unreliable
Healing	Without a scar, unless the dermis is involved	Without a scar
Postmortem production	Readily produced — dragging, ant activity; parchment-like and yellowish	Cannot be produced after death, though lividity closely mimics it — settled by incision

Applied Aspects

Incise every suspected bruise at autopsy; this distinguishes it from postmortem lividity in seconds, and demonstrates the depth and extent, which are often far greater than the surface suggests
Do not date a bruise confidently from its colour; give a wide range, state that colour dating is unreliable, and rely on the presence of yellow as the one reasonably firm indicator that it is more than about 18 hours old
Exclude a bleeding disorder before reporting multiple bruises as assault, particularly in a child; a coagulation screen and a platelet count cost little and prevent a catastrophic error
Look for tramline bruises and fingertip bruises, which are among the few patterns that positively indicate the mechanism, and photograph them with a scale
Remember that a normal abdomen can conceal a ruptured liver; the absence of external bruising does not exclude fatal internal injury, and this is a recurring cause of missed diagnosis in both the living and the dead
Suspect marking nut where lesions itch, are on reachable parts, and fit no weapon; the juice can be identified chemically and the finding usually collapses a false accusation
An abrasion is always at the point of contact, which is what makes it more useful than a bruise for locating the impact — a bruise may have tracked from elsewhere
Nail marks point to the assailant; the concavity of a crescentic abrasion faces the direction the pressure came from, which indicates the position of the hand
Look under the scalp and the abdominal wall at autopsy; both bruise poorly on the surface while concealing severe underlying injury
Photograph dark skin under good light, and use infrared where available; bruises that are invisible clinically may be demonstrable, and their absence from the report is read as their absence in fact
Deep bruises may not appear for a day, so a person examined immediately after an assault should be re-examined and the second examination recorded

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