Injuries & Wound Ballistics
1. What this chapter covers, and how NEET PG actually tests it
Injury questions give a wound description and ask for the weapon, the range, the manner or the legal classification.
The organising principle is that a wound is a record of the force that produced it, so read it backwards.
Every mechanical injury belongs to one of three classes, and the class is decided by how the force met the skin.
| Force | Injury class | Defining feature |
|---|---|---|
| Blunt impact | Abrasion, contusion, laceration | Tissue crushed and torn |
| Sharp edge or point | Incised, stab, chop | Tissue divided cleanly |
| Projectile | Firearm wound | Energy transferred by a moving mass |
The second question follows immediately: what does the wound say about the object, the direction and the time? Those three are what the court actually wants, and every descriptive feature in this chapter exists to answer one of them.
2. Blunt force injuries
2.1 Abrasion
An abrasion is destruction of the superficial epidermis by friction or pressure, and it is the most informative minor injury in forensic practice.
The value of an abrasion is that it is always at the exact site of impact, unlike a bruise, which can migrate.
| Type | Mechanism | Example |
|---|---|---|
| Scratch | Linear, pointed object | Fingernail |
| Graze or brush burn | Tangential friction | Road surface |
| Pressure abrasion | Sustained crushing | Ligature mark |
| Imprint abrasion | Perpendicular impact | Radiator grille, weapon pattern |
An imprint abrasion reproduces the pattern of the object and can identify a specific weapon or vehicle part.
The direction of a graze can be read from the heaped-up epidermal tags, which pile at the far end of the movement.
2.2 Ageing an abrasion
Healing follows a sequence that supports rough dating.
A fresh abrasion is bright red and moist; a scab forms in the first day and is reddish-brown, darkening to brown or black by the second or third day.
Epithelium then grows beneath the scab, which separates around the end of the first week, leaving no scar because the injury is confined to epidermis.
2.3 Contusion
A contusion is extravasation of blood into tissue from ruptured small vessels, with the skin surface intact.
Colour change follows haemoglobin breakdown, and the sequence is the reason a bruise can be dated at all.
| Colour | Approximate age | Pigment |
|---|---|---|
| Red, then purple or blue | Immediate to 3 days | Haemoglobin |
| Bluish-black to brown | 4 days | Haemosiderin appearing |
| Green | 5 to 6 days | Biliverdin |
| Yellow | 7 to 12 days | Bilirubin |
| Normal | About 2 weeks | Cleared |
Colour change begins at the periphery and moves inward, so the margin is older-looking than the centre.
Two traps recur. A contusion can migrate along tissue planes, so a bruise on the forehead can appear as a black eye, and a fracture of the anterior cranial fossa produces spectacle haematoma at a site never struck.
A tramline or railway-line contusion is two parallel bruises with a pale centre, produced by a cylindrical object such as a stick, because the skin is stretched and its vessels torn at the margins of contact while the compressed centre is spared.
Bruising is exaggerated in the very young, the elderly, women, obese people and anyone with a bleeding disorder or on anticoagulants, so the size of a bruise is a poor index of the force applied.
2.4 Laceration
A laceration is a tear produced by blunt force splitting the tissue, and separating it from an incised wound is the commonest single question in the subject.
| Feature | Laceration | Incised wound |
|---|---|---|
| Margins | Irregular, contused, abraded | Clean, sharply defined |
| Tissue bridges | Present across the depth | Absent |
| Hair bulbs | Crushed but often intact | Cleanly cut |
| Foreign material | Common in the wound | Uncommon |
| Bleeding | Less, vessels crushed | More, vessels cleanly cut |
| Dimensions | Variable | Length exceeds depth |
Tissue bridges are the single most reliable discriminator, because blunt force tears the weaker tissue first and leaves tougher strands such as vessels and nerves spanning the gap, while a blade divides everything in its path.
3. Sharp force injuries
3.1 The three types
An incised wound is made by drawing an edge across tissue, and its length exceeds its depth.
A stab wound is made by thrusting a point, and its depth exceeds both its length and its width, which is why a small skin wound can conceal fatal internal injury.
A chop wound is made by a heavy weapon with an edge, such as an axe, and shows features of both classes, with clean margins and underlying bone damage.
3.2 Patterns that indicate the manner
Hesitation cuts, also called tentative cuts, are multiple superficial parallel incisions near a deeper wound, and they indicate a self-inflicted injury.
Defence wounds are on the ulnar border of the forearm and on the palms, produced by warding off or grasping a blade, and they establish that the victim was conscious and resisting.
The cut throat is examined repeatedly because the two manners are distinguishable.
| Feature | Suicidal | Homicidal |
|---|---|---|
| Site | High, above thyroid cartilage | Lower, at or below it |
| Direction | Left to right and downward in a right-handed person | Transverse, often horizontal |
| Depth | Deeper at the start, tailing off | Uniformly deep, may cut both carotids |
| Other wounds | Hesitation cuts | Defence wounds |
| Position of weapon | Present, sometimes gripped by cadaveric spasm | Usually absent |
3.3 Antemortem or postmortem
Wounds inflicted during life bleed freely, gape because of tissue retraction, show clotting and later show inflammatory cellular infiltrate and enzyme change at the margin.
Postmortem wounds bleed little, do not gape, and lack any cellular response.
The distinction matters because injuries are sometimes inflicted after death to disguise the true cause.
4. Firearm injuries
4.1 Weapons and projectiles
Rifled weapons have spiral grooves in the barrel that spin the bullet, giving accuracy and range, and include rifles, revolvers and pistols.
Smoothbore weapons, chiefly shotguns, fire multiple pellets that spread as they travel.
Wounding capacity depends chiefly on the energy delivered.
Because velocity is squared, a small increase in velocity matters far more than a large increase in mass, which is why high-velocity military rifles produce disproportionate injury through temporary cavitation of the tissues around the track.
4.2 Entry and exit wounds
| Feature | Entry | Exit |
|---|---|---|
| Margins | Inverted | Everted |
| Size | Usually smaller | Usually larger and irregular |
| Abrasion collar | Present | Absent |
| Grease or dirt collar | Present | Absent |
| Soot or tattooing | Possible, depending on range | Never |
The abrasion collar forms because the bullet indents and abrades the skin before perforating it, and its presence is close to decisive for an entry wound.
An eccentric abrasion collar indicates an angled shot, and the wider part of the collar lies on the side from which the bullet came.
4.3 Range determination in rifled weapons
This is the highest-yield part of the chapter, because each finding has a different maximum distance.
| Finding | Cause | Approximate limit |
|---|---|---|
| Muzzle imprint, stellate wound over bone | Gas entering and ballooning tissue | Contact |
| Singeing of hair, burning | Flame | About 8 cm |
| Blackening | Soot deposition | About 30 cm |
| Tattooing or stippling | Unburnt powder driven into skin | About 60 to 75 cm |
| Abrasion collar only | The bullet itself | Any distance |
Tattooing cannot be wiped away because the particles are embedded in the dermis, whereas blackening can, and this is the practical bedside test that separates the two.
A contact wound over bone becomes stellate because expanding gases cannot disperse into the tissue and instead balloon the skin against the underlying bone until it splits.
Carboxyhaemoglobin may turn the muscle around a contact wound cherry-pink, since carbon monoxide is a component of the discharge gases.
4.4 Shotgun wounds
Pellets travel together at first and diverge progressively, so the wound reflects the range directly.
At contact and within about a metre there is a single circular hole with clean or scalloped margins, called a rat-hole wound.
Beyond that, the margins become crenated as marginal pellets separate, and further out there are separate satellite pellet holes around a central defect.
As a working rule, the spread of the pellet pattern in inches roughly equals the range in yards, so a fifteen-centimetre spread implies a range of about six yards.
The wad, the disc separating powder from pellets, may be found in the wound at close range and is useful evidence of the cartridge used.
4.5 Residue tests
The dermal nitrate or paraffin test using diphenylamine was once used to show firing residue on the hand, but it reacts with any nitrate, including fertiliser and tobacco, and is now regarded as worthless.
The Walker test detects nitrites in tattooing around a wound and helps establish range.
The Harrison and Gilroy test detects antimony, barium and lead from primer.
Scanning electron microscopy with energy-dispersive X-ray analysis is the modern standard, because it identifies characteristic spheroidal particles containing all three primer metals together, which no ordinary contaminant reproduces.
5. Regional injuries
5.1 Skull fractures
A fissured fracture is a simple linear crack, and is the commonest type.
A depressed or signature fracture reproduces the shape of the striking object, and is produced by a heavy weapon with a small striking surface.
A pond or indented fracture is a shallow dent without a break, occurring in infants because the skull is elastic.
A ring fracture encircles the foramen magnum and follows a fall from height onto the feet or buttocks, transmitting force up the spine.
5.2 Intracranial haemorrhage
Extradural haematoma follows a fracture at the pterion tearing the middle meningeal artery, is biconvex on imaging, and classically shows a lucid interval before deterioration.
Subdural haematoma follows tearing of bridging veins, is crescentic, and is common in the elderly and in alcoholics because cerebral atrophy stretches those veins.
Coup injury is beneath the point of impact and contrecoup is diametrically opposite.
Contrecoup injury predominates when a moving head strikes a fixed object, such as a fall, while coup injury predominates when a moving object strikes a stationary head.
6. Legal classification of hurt
Since the criminal law was recodified, the relevant provisions sit in the Bharatiya Nyaya Sanhita rather than the Indian Penal Code.
Section 114 defines hurt as bodily pain, disease or infirmity caused to any person.
Section 116 designates eight kinds of hurt as grievous, and the list is exhaustive.
| Clause | Grievous hurt |
|---|---|
| a | Emasculation |
| b | Permanent loss of sight of either eye |
| c | Permanent loss of hearing of either ear |
| d | Loss of any member or joint |
| e | Destruction or permanent impairment of the powers of any member or joint |
| f | Permanent disfiguration of the head or face |
| g | Fracture or dislocation of a bone or tooth |
| h | Hurt endangering life, or causing severe bodily pain or inability to follow ordinary pursuits for fifteen days |
Anything not falling within those eight is simple hurt, so the doctor's task is to check the list rather than to judge severity impressionistically.
Note that clause (g) makes any fracture grievous regardless of how trivial it appears, including a chipped tooth, which is a frequent source of error in casualty certificates.
7. Thermal and electrical injuries
7.1 Burns and their medicolegal weight
Burns carry disproportionate importance in Indian forensic practice because of dowry-related deaths, so the central question is usually whether the burning happened before or after death.
Antemortem burns show a red line of vital reaction and blister fluid rich in protein and inflammatory cells, while postmortem burns lack both and any blister contains only air or thin fluid.
Soot in the trachea and bronchi below the level of the larynx, and raised carboxyhaemoglobin in the blood, prove that the victim was breathing in the fire.
Together those two findings are far stronger evidence of being alive than the external appearance of the skin, which can be identical either way.
7.2 Artefacts of burning
Heat stiffening produces the pugilistic attitude, a boxer-like flexed posture caused by protein coagulation and muscle shortening, and it has no relation to the position at death.
Heat rupture of skin resembles a laceration but has no vital reaction, no bleeding and spares the resilient underlying vessels.
Heat haematoma is a collection of blood in the extradural space produced by boiling of blood in the diploe, and can be mistaken for traumatic extradural haemorrhage.
7.3 Electrical injury
The electric mark, or Joule burn, is a firm greyish depressed lesion with raised margins at the point of entry, produced by heating of tissue fluid.
Low-voltage domestic current typically kills by ventricular fibrillation, while high-voltage contact more often kills by respiratory arrest and produces extensive deep burns.
Lightning may leave filigree or arborescent markings, which are not burns but transient vascular patterns, along with magnetisation of metal objects carried on the body.
8. Worked examples
Example 1. A scalp wound has irregular margins, crushed hair bulbs and strands of tissue crossing its depth. What class of weapon caused it?
Tissue bridges and crushed margins mean the tissue was torn rather than divided, so this is a laceration from blunt force. A blade would have cut the bridging vessels and nerves along with everything else.
Example 2. A skin wound shows an abrasion collar, blackening that wipes away, and tattooing that does not. What is the approximate range?
Tattooing means the range was within roughly sixty to seventy-five centimetres. The absence of singeing and of a muzzle imprint places it beyond very close contact, so this is a near shot of a few tens of centimetres.
Example 3. A man has a black eye but no injury to the eyelids, and the forehead shows a healing bruise. How is this explained?
Blood from the forehead contusion has tracked down tissue planes to the periorbital region. This is an ectopic or migratory bruise, and it is why a contusion, unlike an abrasion, does not reliably mark the site of impact.
Summary
Read the wound backwards to the force: blunt force crushes and tears, a sharp edge divides, and a projectile transfers energy.
An abrasion always marks the exact site of impact, and an imprint abrasion can reproduce the pattern of the weapon or vehicle.
A contusion can migrate along tissue planes, so a forehead bruise can appear as a black eye and an anterior fossa fracture as spectacle haematoma.
Bruise colour follows haemoglobin breakdown through biliverdin to bilirubin, changing from the periphery inward, giving green at five to six days and yellow from about a week.
Tissue bridges are the most reliable feature separating a laceration from an incised wound, because blunt force tears the weaker tissue and spares tough strands.
An incised wound is longer than it is deep; a stab wound is deeper than it is long, which is why a small skin wound can hide fatal internal injury.
Hesitation cuts indicate self-infliction and defence wounds on the ulnar forearm and palms indicate resistance.
An entry wound has inverted margins with an abrasion collar; an exit wound has everted margins and never shows soot or tattooing.
Range is read from singeing at about 8 cm, blackening at about 30 cm and tattooing at about 60 to 75 cm; tattooing cannot be wiped away because it is embedded in the dermis.
Shotgun pellet spread in inches approximates the range in yards, and the wad may be recovered at close range.
Modern residue analysis uses scanning electron microscopy with X-ray spectroscopy, since the older dermal nitrate test reacts with any nitrate and is worthless.
Contrecoup injury predominates when a moving head strikes a fixed object, and coup injury when a moving object strikes a stationary head.
Under the Bharatiya Nyaya Sanhita, hurt is defined in Section 114 and the eight kinds of grievous hurt in Section 116, so classification is a matter of checking that list.
In burns, soot below the larynx and raised carboxyhaemoglobin prove the victim was breathing in the fire, and they outweigh any external appearance of the skin.
Pugilistic attitude, heat rupture and heat haematoma are artefacts of burning and must not be read as evidence of a struggle or of head injury.
