Forensic Medicine & Toxicology
High-yield MBBS Forensic Medicine & Toxicology question bank — medical jurisprudence, identification, thanatology, injuries, asphyxia, forensic sexology and toxicology, at Reddy’s / Parikh depth.
12chapters144questions77High-Yield
Definition
Identification is the determination of the individuality of a person, living or dead; corpus delicti means the ‘body of the crime’ — the essential facts proving a crime.
Data Used for Identification
- Race, religion, sex, age, stature, complexion
- Fingerprints — most reliable in the living; DNA profiling — most reliable overall
- Scars, tattoos, moles, deformities, occupational marks
- Teeth, hair, clothing, personal effects, speech, gait, handwriting
- Complete identification — absolute fixation; partial — some data only
Corpus Delicti
- Consists of the body of the victim plus facts proving a crime was committed
- Includes the cause of death and identification of the accused
- Not restricted to the body alone — conviction is possible without a body if other evidence is conclusive
- Destroyed by burning, dissolving in acid, dismemberment or concealment
- Applies in cases of mutilated, decomposed or fragmentary remains, and mass disasters
Identification proceeds from general characteristics to individual features. Method Reliability DNA profiling Absolute Fingerprints Absolute (living) Scars, tattoos Corroborative Applied
- Needed in mass disasters, unknown bodies, impersonation and inheritance disputes
- Doctor gives an opinion; identity is finally decided by the court
🔑KEY POINTS TO REMEMBER- Identification uses race, sex, age, stature, fingerprints, DNA and marks.
- DNA profiling and fingerprints give absolute identification.
- Corpus delicti is the body of the crime — not the corpse alone.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Determination of sex is established from external genitalia in intact bodies and from skeletal features or chromosomes in skeletonised remains.
Skeletal Determination
- Pelvis — most reliable (about 95%): female pelvis is broader, subpubic angle >90°, greater sciatic notch wide, preauricular sulcus present
- Skull — next best (about 90%): male has prominent supraorbital ridges, larger mastoids, square chin
- Long bones — males larger and heavier
- Sternum — male body more than twice the length of the manubrium
- Combined pelvis and skull give about 98% accuracy
Other Methods & Intersex
- Barr body — sex chromatin in female cells (buccal smear); drumstick appendage in neutrophils
- Chromosomal analysis — conclusive; DNA (amelogenin gene)
- Intersex states: gonadal (true hermaphrodite), pseudohermaphroditism, Turner (45,XO), Klinefelter (47,XXY)
- Medicolegal importance: marriage, divorce, inheritance, sports, criminal liability
The pelvis is the single most dependable bone for sexing remains. Feature Male Female Subpubic angle <90° >90° Sciatic notch Narrow Wide Supraorbital ridge Prominent Smooth Applied
- Sex determination of a fetus is prohibited under the PCPNDT Act
- DNA is conclusive when bones are fragmentary
🔑KEY POINTS TO REMEMBER- Pelvis is the most reliable bone (95%); skull next (90%).
- Female pelvis: subpubic angle >90°, wide sciatic notch.
- Barr body and DNA analysis confirm sex when bones are inadequate.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Determination of age uses teeth, ossification of bones and secondary sexual characters, and is of major medicolegal importance.
Age from Teeth
- Temporary (milk) teeth — 20 in number; erupt 6–24 months
- Permanent teeth — 32; first molar at 6 years, second molar at 12 years, third molar (wisdom) 17–25 years
- Gustafson’s method for adults over 25 years
- Teeth are highly resistant to decomposition and fire
Age from Ossification
- Fusion of epiphyses is the key criterion
- Elbow ~16–17 years, wrist ~18 years, shoulder and hip ~18–19 years, knee ~20 years
- Sternal end of clavicle — fuses last, ~21–25 years
- Sacrum fuses about 25 years; skull sutures for later ages
- X-ray of relevant joints is the practical method
Different structures serve as the best indicator at different ages. Age Landmark 6 years First permanent molar 17–18 years Elbow, wrist fused 21–25 years Clavicle (sternal end) Applied
- Criminal responsibility — below 7 years none; 18 years — majority, consent, voting
- Also for marriage, employment, kidnapping, rape and impersonation cases
🔑KEY POINTS TO REMEMBER- Teeth: 20 temporary, 32 permanent; third molar at 17–25 years.
- Epiphyseal fusion: elbow 16–17, wrist 18, knee 20 years.
- Sternal end of clavicle fuses last, at 21–25 years.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Dactylography (fingerprinting) is identification from the ridge patterns of the fingertips — the most reliable method in the living.
Basis & Patterns
- Ridges form by the fourth month of intrauterine life and remain unchanged for life
- No two individuals have identical fingerprints, not even identical twins
- Four main patterns: loops (~65%), whorls (~25%), arches (~7%), composite (~3%)
- Individuality lies in the minutiae (ridge characteristics)
- Galton and Henry systems of classification
Types of Prints & Uses
- Visible (in blood, ink), plastic (in wax, soap), latent (invisible, developed by powders, ninhydrin, iodine, laser)
- Poroscopy — study of sweat pore openings; useful when ridges are fragmentary
- Uses: criminal identification, unknown bodies, impersonation, illiterate persons’ signature (thumb impression), Aadhaar and passports
- Destroyed only by deep dermal injury; regenerate if only epidermis is lost
Permanence and uniqueness together make fingerprints conclusive. Pattern Frequency Loop ~65% Whorl ~25% Arch ~7% Applied
- Prints may be taken from decomposed bodies after glove-of-skin technique
- Legally accepted as conclusive proof of identity
🔑KEY POINTS TO REMEMBER- Fingerprints form by the fourth fetal month and never change.
- Patterns: loops (commonest), whorls, arches, composite.
- Latent prints are developed by powders or chemicals; poroscopy studies sweat pores.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
DNA profiling (DNA fingerprinting) is identification from an individual’s unique DNA sequence — the most reliable identification method available.
Principle & Samples
- Based on variable number tandem repeats (VNTR) and short tandem repeats (STR) in non-coding DNA
- Identical in all nucleated cells of one person; unique except in identical twins
- Samples: blood, semen, hair root, saliva, bone, teeth, tissue
- Mitochondrial DNA — maternally inherited; useful in old, degraded or burnt remains
- Developed by Alec Jeffreys (1985)
Applications & Other Methods
- Paternity and maternity disputes, sexual offences, mass disasters, unknown bodies, exchanged babies, immigration
- Miscellaneous methods: superimposition (skull with photograph), bite marks, handwriting, voice, gait
- Anthropometry (Bertillon system) — obsolete
- Hair and fibre examination; radiological comparison of old fractures and implants
Non-coding repeat regions provide a pattern unique to each person. Method Use STR profiling Routine identification Mitochondrial DNA Degraded remains Superimposition Skull vs photograph Applied
- Chain of custody must be maintained for admissibility
- Identical twins cannot be distinguished by standard DNA profiling
🔑KEY POINTS TO REMEMBER- DNA profiling uses VNTR and STR regions; identical in all body cells.
- Most reliable method except in identical twins.
- Mitochondrial DNA is used for degraded and skeletal remains.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Estimation of stature (height) is used in identification, particularly when only fragmentary remains are available.
Methods in Intact Bodies
- Direct measurement from vertex to heel with the body supine
- Allow for elongation after death — subtract about 2 cm
- Span of outstretched arms ≈ height (fingertip to fingertip)
- Height ≈ 2 × length of one upper limb
- Height ≈ 3.3 × length of sternum; ≈ 8 × length of head
From Long Bones
- Regression formulae — Trotter and Gleser, Karl Pearson formulae
- Femur is the most reliable bone (about 27% of height)
- Tibia, humerus and radius also used, in descending reliability
- Formulae differ by sex, race and side — must use the correct one
- Best measured on a fresh, undamaged bone; accuracy within a few centimetres
Sex and race must be known before the correct formula can be chosen. Bone Reliability Femur Best Tibia Good Humerus Moderate Applied
- Useful in mass disasters and mutilated remains
- Only an approximate range is given, never an exact figure
🔑KEY POINTS TO REMEMBER- Height equals arm span; roughly 3.3 times sternal length.
- Femur is the most reliable bone for stature estimation.
- Trotter and Gleser regression formulae are used, varying by sex and race.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Tattoo marks are designs produced by introducing insoluble pigments into the dermis, and are valuable for identification.
Features
- Pigments: Indian ink (carbon, black), cinnabar (red), cobalt (blue), chromium (green)
- Deposited in the dermis — hence permanent
- Pigment is also carried to regional lymph nodes — detectable even after the skin tattoo is removed
- May indicate religion, caste, occupation, regiment, name or relationships
- Fade with time; cinnabar (red) is most easily removed, black most persistent
Medicolegal Importance
- Aid identification of living persons and unknown bodies
- Persist after putrefaction — may be visible after removing the epidermis
- Removal by excision, laser, dermabrasion or caustics leaves a scar
- Criminals may deliberately obliterate tattoos — examine lymph nodes
- Rarely transmit hepatitis B, C and HIV if unsterile needles are used
Pigment in regional nodes survives even after the tattoo is erased. Pigment Colour Persistence Indian ink Black Longest Cinnabar Red Fades easily Cobalt Blue Moderate Applied
- Photograph tattoos before autopsy
- Examine axillary or inguinal nodes if a tattoo appears removed
🔑KEY POINTS TO REMEMBER- Tattoo pigment is deposited in the dermis, making it permanent.
- Pigment also travels to regional lymph nodes — useful after removal.
- Indicate religion, occupation or relationships; red fades most easily.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
A scar is fibrous tissue replacing normal tissue after healing of a wound extending into the dermis, and is useful for identification.
Characteristics
- Formed only when the wound involves the dermis — superficial abrasions leave none
- Recent scar — red, soft, tender; old scar — white, glistening, avascular, contracted
- Permanent, though it may become inconspicuous
- No hair follicles, sweat or sebaceous glands; no pigment
- Keloid — extends beyond the wound margin; hypertrophic scar stays within
Medicolegal Importance
- Identification of living persons and unknown bodies
- Site suggests the nature of the injury — vaccination, surgery (linear), burns (irregular contracted), whipping
- Age of the scar gives approximate time of the injury
- Corroborates the history in assault or accident claims; insurance and compensation
- Deliberate scarring may be used to fake or conceal identity
Only dermal injury produces a lasting scar. Age Appearance Recent Red, soft, tender Few months Pale, firm Old White, glistening Applied
- Surgical scars may reveal past operations in an unknown body
- Scars cannot be dated precisely — only approximately
🔑KEY POINTS TO REMEMBER- Scars form only when the dermis is involved and are permanent.
- Recent scars are red and tender; old scars white and glistening.
- Shape and site indicate the nature of the original injury.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Gustafson’s method estimates age in adults over 25 years from regressive (age-related) changes in a single tooth.
The Six Criteria
- Attrition (A) — wear of the occlusal surface
- Periodontosis (P) — recession of the gum and periodontal attachment
- Secondary dentine (S) — deposition within the pulp cavity
- Cementum apposition (C) — added at the root
- Root resorption (R) — at the apex
- Root transparency (T) — the most reliable single criterion
Technique & Value
- A ground longitudinal section of the tooth is examined
- Each criterion scored 0 to 3; total points plotted on a regression formula
- Age estimated within about ± 3–7 years
- Applicable only after 25 years, when eruption and epiphyseal methods have ended
- Teeth resist fire, decomposition and trauma — useful in charred and skeletal remains
Scoring several age-related changes together improves accuracy. Criterion Note Root transparency Most reliable Attrition Diet-dependent Score range 0–3 each Applied
- Especially valuable in mass disasters and unidentified skeletons
- Attrition varies with diet, so results are approximate
🔑KEY POINTS TO REMEMBER- Gustafson’s method estimates adult age above 25 years from one tooth.
- Six criteria: attrition, periodontosis, secondary dentine, cementum, resorption, transparency.
- Root transparency is the most reliable; accuracy about ± 3–7 years.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Superimposition is a technique of identification in which a photograph of the skull is superimposed on an antemortem photograph of the suspected person.
Technique
- Requires a recovered skull and a good antemortem photograph of the suspect
- Skull photographed at the same angle, orientation and magnification as the photograph
- Images superimposed using video, photographic or computer techniques
- Landmarks matched: outer canthi, nasion, glabella, teeth, chin, external auditory meatus, hairline
- Also called craniofacial superimposition
Value & Limitations
- Provides negative (exclusionary) evidence with certainty — mismatch excludes identity
- A match is only corroborative, not conclusive
- Best combined with DNA or dental comparison
- Famous example: the Ruxton case (1935), the first successful use
- Limitations: poor-quality or old photographs, damaged skull, soft-tissue variation
The technique excludes with certainty but confirms only tentatively. Result Value Mismatch Excludes identity Match Corroborative only Applied
- Useful when only a skull is recovered and DNA is unavailable
- Facial reconstruction is an alternative approach
🔑KEY POINTS TO REMEMBER- Superimposition matches a skull photograph with an antemortem photograph.
- Exclusion is conclusive; a match is only corroborative.
- First used successfully in the Ruxton case (1935).
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Anthropometry, or the Bertillon system, is identification by recording a set of body measurements — the first scientific method of criminal identification.
Principle & Measurements
- Introduced by Alphonse Bertillon in 1882 in Paris
- Based on the premise that bony dimensions do not change after 21 years
- Eleven measurements recorded: height, sitting height, arm span, length and breadth of head, length of left foot, left middle and little finger, left forearm, length and breadth of right ear
- Also recorded eye colour, complexion, scars and marks (portrait parlé)
Limitations & Present Status
- Time consuming and requires trained personnel
- Not applicable below 21 years (bones still growing)
- Errors of measurement; measurements may coincide in different persons — not individually unique
- Replaced by fingerprinting, which is quicker and absolute
- Now obsolete, though of historical importance; principles survive in forensic anthropology
Measurements can coincide between people, unlike fingerprints. Feature Detail Introduced Bertillon, 1882 Measurements Eleven Status Obsolete Applied
- Historical significance as the first scientific identification system
- Superseded because fingerprints are unique and easily recorded
🔑KEY POINTS TO REMEMBER- Anthropometry (Bertillon, 1882) used eleven body measurements.
- Based on the fixity of bone dimensions after 21 years.
- Now obsolete, replaced by fingerprinting.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Forensic odontology uses teeth and bite marks for identification, since the dental pattern of every individual is unique.
Dental Identification
- Teeth are the hardest and most durable tissues — resist fire, decomposition and immersion
- Comparison of antemortem dental records with postmortem findings
- Notes missing teeth, fillings, crowns, prostheses, caries, malalignment
- Useful in mass disasters, charred bodies and skeletal remains
- Teeth also yield DNA from pulp
Bite Marks
- Found in sexual offences, child abuse, assault and on food items at crime scenes
- Appear as paired opposing semicircular (horseshoe) abrasions or bruises
- Photographed with a scale; casts and swabs taken (saliva for DNA)
- Compared with the suspect’s dental cast
- Human bites are shallow and semicircular; animal bites are deeper and narrower with pointed canine punctures
Saliva recovered from a bite mark often gives a DNA profile. Feature Human Animal Shape Semicircular Narrow, V-shaped Depth Shallow Deep punctures Applied
- Bite marks change with time — photograph promptly and repeatedly
- Saliva swab before washing the area
🔑KEY POINTS TO REMEMBER- Teeth are the most durable tissue and unique to each person.
- Dental record comparison identifies charred and skeletal remains.
- Bite marks are photographed with a scale; saliva swab gives DNA.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.