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Coup and Contrecoup Lesions

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Definitions

• The Essentials of Forensic Medicine and Toxicology (2026): "Coup (blow; impact) means that the injury is located beneath the area of impact and results directly by the impacting force. Contrecoup means that the lesion is present in an area opposite the side of impact."

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Mechanism

Coup Injury

• Occurs when a moving object strikes a stationary head (e.g., being hit by a bat)
• The brain tissue directly under the point of impact is bruised/contused
• Also occurs at the impact site when a blow fractures the skull, producing local shear strain

Contrecoup Injury

• Occurs when a moving head decelerates suddenly by hitting a firm surface (e.g., falling and striking the ground)
• The brain, still in motion due to inertia, continues moving inside the skull and strikes the opposite inner wall
• This rebound impact typically produces more severe injury than the coup injury

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Theories Explaining Contrecoup Injury

1. Struck Hoop Theory - The skull flattens at the impact site, briefly assuming an ovoid shape, transmitting force to the opposite side of the brain.
2. Russell's Theory - The brain suddenly displaces toward the impact site like a jelly mass, creating a potential space on the opposite side that injures vessels, causing subdural and cortical injuries.
3. Gaggio's Pressure Gradient Theory - At the moment of impact, positive pressure builds on the impact side and negative pressure on the opposite side; this negative pressure ruptures vessels on the contrecoup side.
4. Holbourn's Shear Strain Theory (most accepted) - Rotational forces from the blow cause shear strains - adjacent brain particles slide against each other. The rotational velocity change is greater at the pole opposite the impact, making contrecoup injuries more extensive.
5. CSF Density Theory - The brain is less dense than CSF. During rapid deceleration, denser CSF moves toward the impact site, displacing the lighter brain in the opposite direction, causing it to strike the contralateral skull.
6. Rawling's Theory of Bony Irregularities - Irregular bony prominences (orbital plates, cribriform plate, lesser wings of sphenoid) lacerate/contuse the base of the frontal lobes and tips of temporal lobes.

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Important Practical Points

1. Sometimes only contrecoup injury exists with no coup damage at all - this is actually the more common pattern after falls
2. Skull fracture is NOT required - severe coup and contrecoup injuries can occur with an intact skull
3. Contrecoup injury is more extensive - when both are present, contrecoup is always more severe than coup
4. Most common sites for contrecoup injury are the frontal lobe poles (especially after a fall on the occiput) and temporal lobe tips
5. A fall on the occiput causes contrecoup in the frontal lobes (often bilateral/symmetrical)
6. A fall on the frontal region virtually never produces occipital contrecoup - this is an asymmetry important in forensic analysis
7. In temporal/parietal impact, contrecoup is diametrically opposite on the contralateral hemisphere
8. Contrecoup injuries manifest as cortical contusions, lacerations, subdural, or subarachnoid hemorrhage
9. Severe frontal contrecoup from an occipital fall can fracture the thin orbital plate floor, causing blood to track into the orbits as "black eyes" (raccoon eyes)
10. Contrecoup injuries are rare before age 3 - likely because the young brain fits the skull more tightly

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Forensic Significance

• The location of coup vs. contrecoup lesions helps reconstruct the direction and nature of the blow
• A line drawn between the centers of coup and contrecoup indicates the direction of impact relative to the head
• Finding only contrecoup without coup suggests the head was moving (a fall), not struck by an object
• If an assault victim shows only contrecoup injuries, it may suggest they fell after being struck rather than being directly hit on that side

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Cardinal Signs of Death Due to Starvation

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A. Clinical Signs (Antemortem)

General Appearance

• Extreme emaciation - progressive loss of body weight; death typically occurs when 35-50% of original body weight is lost
• Loss of subcutaneous fat - bones become prominent; ribs visible with concavities in intercostal spaces; sunken supraclavicular fossae
• Limbs like broomsticks - arms and legs extremely thin and flaccid
• Concave abdomen - sunken from costal margins to iliac crests (scaphoid abdomen)

Face & Head

• Eyes sunken and glistening with dilated pupils
• Cheeks hollow - Bichat's buccal pad of fat is among the last subcutaneous fat to disappear (important forensic point)
• Lips dry and cracked
• Tongue coated, dirty, intolerable thirst
• Saliva thick and scanty
• Voice feeble, almost a whisper
• Hair dry, lustreless, brittle; nails brittle and ridged

Skin

• Dry, rough, thin, inelastic, wrinkled and pigmented (brown discolouration)
• Drawn tight like parchment over bony prominences
• Sometimes fissured and ulcerated from superadded infection
• Offensive body odour
• Oedema (from hypoproteinaemia) may occur and can mask the degree of weight loss

Systemic Features

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B. Postmortem (Autopsy) Findings

External Findings

• Extreme emaciation with complete absence of subcutaneous fat
• Muscles flabby and greatly reduced in size
• Rigor mortis comes on early and lasts a short time (due to reduced tissue vitality)
• Decomposition sets in early
• Pressure sores may be present
• Dental caries (especially in children)

Internal Findings - The Cardinal Triad

The three characteristic postmortem findings that are pathognomonic of starvation (Parikh's):

1. Almost complete disappearance of body fat - not seen in any wasting disease. Omental and mesenteric fat entirely absent.
2. Disuse atrophy of the digestive tract - the small intestine may be so thin as to be almost transparent (considered the single most typical sign of starvation)
3. Distension of the gallbladder - filled and distended due to accumulation of bile, as there has been no food stimulus to empty it. Gallstones may be present.

Other Internal Findings

• General reduction in weight of all organs except the brain - the brain is spared (organs weighed at autopsy and compared to age/sex standard tables)
• Heart, liver, spleen, kidneys - all atrophied and pale
• Serous atrophy of fat around the heart and in bone marrow (replaced by gelatinous tissue)
• Lungs - pale, small, exude very little blood when cut
• Blood volume reduced; marked anaemia
• Stomach empty; may be no wider than ordinary colon
• Large bowel may contain faecoliths and non-specific ulcerations ("pseudo-dysentery")
• Urinary bladder practically empty
• Bones demineralised - areas of rarefaction on X-ray; in adults, progressive osteomalacia; in children, rickets, spinal curvature, dental defects
• Peritoneal and pleural effusions may be present

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C. Cause of Death

• Acute starvation - death from inanition and circulatory failure
• Chronic/partial starvation - reduced vitality leads to death from intercurrent infection (the most common terminal event)
• Direct causes: infections, cardiac arrhythmias, hypoglycaemia

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D. Fatal Period

• Females withstand starvation better than males (more body fat)
• The very young and the elderly suffer most
• Cold weather hastens death from starvation

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E. Medicolegal Importance

• Death due to starvation can be suicidal (hunger strike, anorexia nervosa), homicidal (child abuse, neglect of dependents - "baby-farmers"), or accidental (famine, entrapment)
• In criminal cases, the victim (usually child or female) may have food in the stomach - a "grim last meal" given to avert suspicion
• The forensic pathologist must exclude wasting diseases (cancer, dementia, TB) before certifying starvation as the cause of death

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Forensic Medicine - Exam Answers (As per Reddy)

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Q1. Define Medical Jurisprudence [5 Marks]

• Medical negligence cases
• Consent for medical treatment
• Rights and duties of doctors
• Serious professional misconduct
• Medical ethics and etiquette
• Issues involving mental competence, age, identity, etc.

In short: It deals with the LEGAL ASPECTS of the PRACTICE OF MEDICINE.

• Forensic Medicine deals with medical aspects of law (applying medical knowledge to legal problems - murder, injuries, sexual offences, poisoning)
• Medical Jurisprudence deals with legal aspects of medical practice (doctor's duties, professional conduct, negligence)

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Q2. What do you mean by BMDC & BMA? [5 Marks]

BMDC - Bangladesh Medical and Dental Council

• The BMDC is the regulatory body for medical and dental practitioners in Bangladesh
• Established under the Bangladesh Medical and Dental Council Act
• Functions:
  1. Maintains a register of qualified medical and dental practitioners
  2. Sets minimum standards for medical and dental education
  3. Grants recognition to medical colleges and their degrees
  4. Issues registration certificates to qualified practitioners
  5. Has authority to take disciplinary action and remove names from the register for infamous conduct (serious professional misconduct)
  6. Prescribes the code of medical ethics for practitioners in Bangladesh
• Every medical practitioner must be registered with the BMDC to legally practice medicine in Bangladesh

BMA - Bangladesh Medical Association (or British Medical Association)

• Bangladesh Medical Association (BMA): The professional association/trade union of medical doctors in Bangladesh. It is a voluntary body (unlike BMDC which is statutory).
  • Protects the professional interests of doctors
  • Promotes the cause of medicine and public health
  • Provides a platform for scientific discussion and continuing medical education
  • Negotiates service conditions for doctors
  • Publishes medical journals and guidelines

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Q3. Define Medico-Legal Autopsy [5 Marks]

Definition of Medico-Legal Autopsy:

Distinguishing Features (Reddy):

1. Clinical history is often absent, sketchy, doubtful or misleading
2. Identity of the deceased may not be known
3. The pathologist must determine time of death and age of injuries
4. Must determine cause, manner (natural/accidental/suicidal/homicidal) and mechanism of death
5. Must carry out careful external examination including clothing
6. Determines the pattern of injuries and their relationship to the causative weapon
7. Must collect trace evidence
8. Has evidentiary and confirmatory value for public interest
9. If inconsistencies exist between death scene and findings, must visit the scene of crime

When is a medico-legal autopsy ordered?

• Homicide or suspected homicide
• Suicide or suspected suicide
• Accidental death
• Sudden/unexpected death
• Death in police custody
• Death of unknown cause
• Death of medically unattended persons
• Death due to medical negligence

Legal basis (Bangladesh):

"A complete autopsy is necessary to substantiate the truth as corroborative evidence of eyewitnesses. A poor or incomplete autopsy is worse than no autopsy at all, as it is more likely to lead to a miscarriage of justice." - Reddy

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Q4. Define Laceration. Mention Its Types [5 Marks]

Definition:

• If underlying tissue is rigid (e.g., skull beneath scalp) → laceration occurs readily and may simulate an incised wound
• If underlying tissue is flexible (e.g., cheek, soft parts of limbs) → laceration is jagged and irregular

Types of Lacerations (Reddy/Parikh):

• Caused by blunt perpendicular impact
• Skin crushed between two hard surfaces (bone + weapon)
• Seen over scalp, face, hands, lower legs
• Mimics an incised wound but shows tissue bridges on close examination
• Most common forensically significant type

• Due to over-stretching of skin until it splits, producing a flap
• Caused by blunt tangential impact
• The flap indicates the direction of force/vehicle
• Seen in run-over injuries; can occur from kicking or fracture

• Caused by shearing/grinding force at an acute angle
• Tears off (detaches) a portion of skin/tissue from its attachments
• Lorry wheel running over a limb causes skin separation over large area = "Flaying"
• Underlying muscles crushed, bones may fracture

• Produced by irregularly directed impact
• Irregular, jagged edges

• Impact exceeds tensile strength of an internal organ
• Laceration of liver, spleen, etc. without external tear
• Seen in blunt abdominal trauma

Characteristics of all lacerations:

• Irregular, ragged, and contused margins
• Tissue bridges (strands of tissue) crossing the wound
• Hair bulbs crushed (not cut)
• Contamination with foreign material
• Adjacent bruising and abrasions

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Q5. What are the Causes of RTAs (Road Traffic Accidents)? [5 Marks]

A. Human Factors (Most Important - ~80-85% of accidents)

1. Speeding - most common cause
2. Drunken driving / driving under influence of drugs
3. Reckless and negligent driving
4. Overtaking - dangerous/improper overtaking
5. Fatigue and drowsiness - long-haul drivers
6. Distraction - mobile phone use, talking, eating while driving
7. Inexperience - young drivers, unlicensed drivers
8. Non-adherence to traffic rules - jumping red lights, wrong lane driving
9. Medical conditions - epilepsy, sudden cardiac event, visual impairment
10. Pedestrian error - jaywalking, sudden crossing

B. Vehicle Factors

1. Brake failure
2. Tyre burst/blowout - especially at high speed
3. Steering defects
4. Faulty headlights - poor night visibility
5. Overloading - especially of trucks/buses
6. Poor vehicle maintenance

C. Road/Environmental Factors

1. Poor road condition - potholes, uneven surface, sharp curves
2. Inadequate road lighting
3. Absence of road signs and signals
4. Fog, rain, mist - reduced visibility
5. Slippery roads - rain, oil spills
6. Narrow roads
7. Non-segregation of pedestrians and vehicles

D. Other Factors

• Stray animals on road
• Road construction zones
• Absence of median dividers

Reddy notes the "Haddon matrix" concept - interaction of host (driver/pedestrian), agent (vehicle) and environment (road/climate) as the basis of RTA causation.

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Q6. Differences Between Somatic Death and Molecular Death [5 Marks]

Additional Notes (Reddy):

• Apparent death (Suspended animation) - may mimic somatic death but is reversible (e.g., drowning, electrocution, hypothermia) - must be distinguished before certifying death
• Molecular death is the basis for organ and tissue transplantation - organs must be harvested between somatic and molecular death
• Post-mortem changes (rigor mortis, livor mortis) begin after somatic death but represent continuing molecular processes

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Q7. Differences Between Hanging and Strangulation [5 Marks]

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Q8. Lung Findings During Autopsy in Case of Infanticide [5 Marks]

A. Docimasia (Hydrostatic Test / Lung Float Test)

1. Remove lungs with heart and thymus en bloc
2. Place in a vessel of water
3. If they float → baby breathed (live birth)
4. If they sink → stillborn (did not breathe)
5. Separate the two lungs and repeat
6. Cut each lung into small pieces and test each piece

B. Macroscopic Findings in the Lungs

• Lungs are pink, spongy, soft, and crepitant on palpation
• Fill the chest cavity and overlap the pericardium
• Weight: approximately 50-60 grams (both lungs)
• Specific gravity < 0.9 (less than water) → floats
• Margin of lungs are rounded and puffy
• Surface shows marked mottling (areas of pink and dark red)
• On section, frothy blood-stained fluid oozes out

• Lungs are dark red, solid, non-crepitant, liver-like in consistency
• Occupy only the upper portion of chest, do not overlap pericardium
• Specific gravity > 1.0 (heavier than water) → sinks
• Weight: approximately 30-40 grams
• Smooth, homogeneous surface - no mottling

C. Microscopic Findings

• In aerated lungs: alveoli are expanded, walls stretched and thin, air spaces present
• In stillborn: alveoli collapsed with cuboidal/columnar epithelium (foetal type)

D. Limitations of Hydrostatic Test (Reddy emphasizes)

1. Putrefaction - gases of decomposition can cause unaerated lungs to float → false positive
2. Artificial respiration given after birth can aerate lungs
3. Premature babies may have partially aerated lungs
4. Inhalation of meconium or fluid may partially aerate lungs without true breathing

E. Other Lung Findings in Infanticide (Smothering/Suffocation)

• Tardieu's spots (petechial haemorrhages) on pleural surfaces - classic asphyxial sign
• Pulmonary oedema and congestion
• Areas of atelectasis

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Q9. Entry Wound in Close-Range Rifled Firearm Injury [5 Marks]

Definition of Close-Range Shot:

Features of Entry Wound in Close-Range Rifled Firearm Injury:

A. Shape

• Round or oval - due to the pointed, high-velocity bullet from a rifled weapon

B. Size

• Slightly smaller than the calibre of the bullet due to skin elasticity (skin contracts after bullet passes)
• May be exact calibre size or slightly larger if bullet is tumbling

C. Abrasion Collar (Graze/Contusion ring) - MOST IMPORTANT

• A ring of abraded skin surrounds the entry wound
• Caused by the bullet stretching and wiping the skin as it enters
• Also called contusion ring, marginal abrasion, or collar of dirt
• Width: 1-3 mm
• Pathognomonic of entry wound

D. Blackening/Soot Deposition (Fouling)

• At close range: Blackening/soiling (soot) is deposited on the skin AROUND the wound
• Soot can be wiped off (differentiates from tattooing)
• Pattern: diffuse blackening that gets wider as range increases (up to ~30 cm)

E. Tattooing (Stippling)

• Unburnt/partially burnt powder particles penetrate the skin and cannot be wiped off
• Present at close range (15-30 cm depending on weapon/ammunition)
• Individual punctate marks in a zone around the wound
• Cannot be wiped off (distinguishes from blackening)
• Pattern of tattooing helps estimate the range of fire

F. Burning/Singeing

• At very close range: burning and singeing of skin hairs around the wound
• Flame from muzzle may cause singing or charring of the wound edges

G. Wound Margins

• Relatively clean and inverted (punched-in appearance)
• Edges are inverted inward (pushed in by the bullet)
• Contused/bruised margins

H. No Tailing

• No "tailing" (unlike entry wounds from tangential shots)

I. Internal Findings

• Bullet wipe - ring of dirt/grease deposited around the edges inside the wound tract
• Primary wound track with haemorrhage, tissue disruption, and cavitation

Summary Table: Close-Range vs Other Ranges

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Q10. How to Estimate 3% Burn? [5 Marks]

Rule of Nines (Wallace's Rule of Nines)

Modification in children: In children the head is proportionally larger. Lund and Browder chart is more accurate for children under 10.

Estimating 3% Burns:

• The patient's own palm (with fingers together) ≈ 1% of their TBSA
• Therefore: 3% burn = area equivalent to 3 palms of the patient
• This is the simplest and most practical bedside method for small, scattered or irregular burns

• A more detailed anatomical chart dividing body into smaller segments
• Most accurate method, especially in children
• Accounts for age-related differences in proportion

Medicolegal Importance of Burn Area Estimation (Reddy):

• Burns <15% TBSA in adults (or <10% in children/elderly) = Minor burns (usually survive without complications)
• Burns >50% TBSA = high mortality (usually fatal)
• Burn area determines:
  1. Fluid resuscitation requirements (Parkland formula: 4 mL × kg × %TBSA)
  2. Prognosis and medicolegal assessment
  3. Degree of grievous hurt for legal certification (burns >30% = grievous hurt under BNS)

Specific Estimation of Exactly 3%:

• 3% = approximately three palms of the patient's own hand
• In a 70 kg adult: 3% TBSA = approximately 2,100 cm² (since total body surface ≈ 1.7 m²)
• Or: roughly half the anterior surface of one forearm

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