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Forensic Medicine & Toxicology (FMT) - Complete Notes

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1. Estimation of Time Since Death (PMI - Postmortem Interval)

Methods Used

• After death, body temperature falls at approximately 1.5°F (0.83°C) per hour under average conditions.
• The rate is affected by: ambient temperature, clothing/covering, body fat, air circulation, humidity.
• A warm body is not necessarily recently dead - always correlate with other findings.

• Appears at ~1-2 hours, fully formed at ~12 hours, sustained for next 12 hours, disappears over next 12 hours ("march of rigor").
• Order of appearance: eyelids → neck/lower jaw → chest → upper limbs → abdomen → lower limbs → fingers and toes (proximal to distal, small muscles first).
• Disappearance follows the same order.
• Mechanism: After death, aerobic respiration ceases. Anaerobic glycolysis depletes ATP. Without ATP, actin-myosin cross-bridges cannot detach, causing muscle rigidity. Proteins then autolyze (via lysosomal enzymes) and secondary flaccidity sets in at ~36 hours.

• Cornea becomes cloudy within 2-3 hours (faster in open eyes).
• Tache noire (desiccation of cornea): black horizontal band on sclera in open-eyed bodies.
• Potassium in vitreous humor increases at a known rate (~1 mmol/L per 5 hours) - can give a chemical estimate of PMI.

• Gastric emptying time of ~4-6 hours can help correlate last meal timing with time of death.

• Blow fly (Calliphora) eggs on body within minutes to hours of death; successive insect succession patterns can estimate PMI over days to weeks.

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2. Rigor Mortis vs. Cadaveric Spasm (Classic Distinction)

Key exam point: Cadaveric spasm cannot be produced after death - it occurs at the instant of death and goes directly into the rigor mortis phase. This distinguishes it from ordinary rigor mortis and proves the person was alive when they gripped the object.

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3. Postmortem (PM) Lividity vs. Contusion (Classic Distinction)

Key exam points:

• Lividity in atypical location (e.g., on the back in a body found face down) = body was moved after death.
• The "incision test" is the classic distinction: lividity - fluid blood drains; contusion - stained infiltrated tissue remains.
• Pink/cherry-red lividity = CO poisoning or cyanide. Pale lividity = severe anemia or blood loss.

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4. Putrefaction

Stages and Timeline

• Autolysis begins (self-digestion by intracellular enzymes)

• Green discoloration first appears in the right iliac fossa (cecum/ascending colon area, rich in bacteria) - the earliest external sign of putrefaction
• Spreads to rest of abdomen, face, then whole body

• Gas formation (H₂S, CH₄, NH₃, CO₂) causes bloating of abdomen and face
• Marbling: gas tracking under skin along blood vessels, producing greenish-black tree-like pattern
• Bullae (large skin blisters filled with foul-smelling fluid) form
• Eyes and tongue protrude; face becomes unrecognizable
• Body odor becomes intense

Factors Affecting Rate

• Accelerating: High temperature, moisture, presence of infection/sepsis, obesity, trauma/wounds, insects
• Delaying/Arresting: Cold temperature, dry air, burial in dense soil, submersion in water (slows but doesn't stop), antiseptic poisoning

Special Preservation Forms

MLI of Putrefaction

• Establishes body has been dead for some time
• Adipocere formation can allow identification of sex and injuries weeks to years later
• Putrefaction displaces rigor mortis

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5. Medical Legal Importance (MLI) of Age

Why Age Matters Legally

Exam focus points:

• 7 years - no criminal responsibility
• 12 years - consent becomes qualified; rape clause
• 16 years - kidnapping for boys; POCSO threshold discussions
• 18 years - female marriage, majority, valid consent
• 21 years - male marriage, guardianship majority

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6. Dactylography

Fundamental Properties of Fingerprints (Galton's Principles)

1. Individuality - No two individuals (including identical twins) have the same fingerprint pattern
2. Permanence - Patterns form at 10-16 weeks of gestation and remain unchanged throughout life and after death (until putrefaction destroys them)
3. Infallibility - Cannot be altered voluntarily (deliberate destruction results in regeneration of the same pattern)

Types of Fingerprints Found at Crime Scenes

Classification of Fingerprint Patterns (Henry System / Galton)

Ridge Characteristics (Minutiae) - Galton's Details

• Ridge endings, bifurcations (forks), dots, short ridges, enclosures, bridges, spurs, crossovers

Development Methods for Latent Prints

• Physical: Fingerprint powder (aluminum/lamp black/fluorescent) + brush; vacuum deposition
• Chemical: Ninhydrin (reacts with amino acids in sweat); Iodine fuming; Silver nitrate; Cyanoacrylate (superglue) fuming
• Biological: Luminescent stains (DFO)

Medico-Legal Importance of Dactylography

1. Personal identification - Most reliable method; used in criminal investigation, civil cases (immigration, property), and identification of unknown bodies
2. Criminal identification - Matches crime scene prints with suspects; admissible court evidence
3. Paternity disputes - Fingerprint ridge patterns have hereditary component
4. Identification of burned/decomposed bodies - Prints may survive when other features are destroyed
5. Genetic conditions - Altered ridge patterns in chromosomal disorders (Down syndrome - simian crease + single transverse crease), congenital rubella
6. Newborn identification - Foot/palm prints used for hospital records
7. Banking and security - Biometric authentication

Historical Pioneers

• Francis Galton (1892): First classified fingerprints; established individuality and permanence
• Sir Edward Henry: Developed the Henry Classification System (basis of modern 10-digit fingerprint ID)
• Juan Vucetich: Parallel classification system used in South America
• Sir William Herschel: First practical use of fingerprints for identity verification (India, 1858)
• Dr. Henry Faulds: Proposed fingerprint identification to Scotland Yard

Automated Systems

• AFIS (Automated Fingerprint Identification System) - Database matching
• IAFIS (Integrated AFIS) - FBI's national database

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Sources: Guyton & Hall Textbook of Medical Physiology (Rigor Mortis - ATP/cross-bridge mechanism); StatPearls - Postmortem Changes (NCBI); Pacoroners.org - Postmortem Changes and Time of Death; Forensic Medicine sources (Reddy, Parikh); Indian Penal Code & related legislation for MLI of Age.