Para-Clinical Forensic Medicine and Toxicology Syllabus

State the classic formula used to estimate the time since death from body temperature.

$$\text{Time since death (hours)} = \frac{\text{Normal body temp} - \text{Rectal temp}}{\text{Rate of cooling per hour}}$$ using a normal body temperature of $98.6\,^\circ\text{F}$ and an average rate of about $1.5\,^\circ\text{F/hr}$.

Define Rigor Mortis and describe its typical onset and duration in a temperate climate.

Rigor mortis is post-mortem stiffening of muscles due to depletion of ATP and accumulation of lactic acid, causing actin-myosin binding. It usually begins 1-2 hours after death, is complete in about 12 hours, remains for about 12 hours, and passes off in the next 12 hours ('rule of 12').

What is Livor Mortis (post-mortem lividity/hypostasis) and its medico-legal importance?

Livor mortis is the bluish-purple discoloration of dependent parts of the body due to settling of blood after circulation stops. It begins within 1-3 hours, fixes by 6-8 hours, and helps estimate time since death and whether the body was moved after death.

Contrast the color of post-mortem lividity in carbon monoxide poisoning vs cyanide vs hydrogen sulfide poisoning.

Carbon monoxide: cherry-red/pink; Cyanide: bright cherry-red/pink; Hydrogen sulfide: bluish-green/greenish; Nitrites/aniline (methemoglobinemia): brown/chocolate.

Define Cadaveric Spasm (instantaneous rigor) and its medico-legal significance.

Cadaveric spasm is instantaneous stiffening of a group of voluntary muscles at the moment of death without a preceding stage of primary flaccidity, seen in situations of extreme emotion/exertion. It cannot be reproduced artificially, so it indicates the deceased's activity at the instant of death (e.g., weapon grasped in hand suggests suicide).

Differentiate a Medico-Legal autopsy from a Clinical (pathological) autopsy.

Medico-legal (forensic) autopsy: ordered by legal authority, consent not required, aims to establish cause/manner of death and identity, whole body examined, chain of custody maintained. Clinical/pathological autopsy: performed for academic reasons, requires next-of-kin consent, focuses on disease/diagnosis.

Name the three classic incisions used to open the body in an autopsy.

The I-shaped (straight) incision, the Y-shaped incision, and the modified Y-shaped incision (from behind each ear to mid-clavicle to pubic symphysis).

Define 'cause of death', 'mechanism of death', and 'manner of death'.

Cause of death: the disease/injury responsible for starting the lethal sequence (e.g., gunshot wound). Mechanism of death: the physiological derangement producing death (e.g., hemorrhage). Manner of death: the way death came about — natural, accidental, suicidal, homicidal, or undetermined.

Classify mechanical injuries (wounds) into their main types.

Blunt force: abrasions, contusions (bruises), lacerations. Sharp force: incised wounds and stab (punctured) wounds. Also firearm injuries and regional injuries. (Chop wounds combine blunt and sharp force.)

Differentiate an incised wound from a laceration.

Incised (cut) wound: caused by a sharp-edged weapon; clean, regular margins; length > depth; no tissue bridging; ends tapering. Laceration: caused by blunt force; irregular, ragged margins; tissue bridging present; abraded/bruised margins; hair bulbs intact.

How do you distinguish an entry wound from an exit wound in a firearm injury?

Entry wound: usually smaller, inverted (inturned) margins, abrasion collar/grease collar present, tattooing/blackening if close range. Exit wound: usually larger, irregular, everted (outturned) margins, no abrasion collar, no tattooing.

Estimate firearm range from close/contact wound characteristics.

Contact: muzzle imprint, cherry-red/blackened, cruciate/stellate tear (over bone). Close range (within a few cm): blackening (soot), tattooing/stippling present, singeing/burning of hair. Distant (beyond ~1 m for handgun): only the bullet wound, no tattooing or blackening.

Define 'abrasion' and state its medico-legal importance.

An abrasion is a superficial injury involving the destruction of the superficial epidermis by blunt friction. Importance: indicates site of impact, gives patterned impression of the causative object (patterned abrasion), and helps determine direction of force.

How does the colour change of a bruise help estimate its age?

Red (fresh) → bluish (few hours to days) → brownish/greenish (~4-7 days, biliverdin) → yellowish (~7-12 days, bilirubin/hematoidin) → normal (~2 weeks). Sequence reflects hemoglobin breakdown.

Differentiate an ante-mortem wound from a post-mortem wound.

Ante-mortem: signs of vital reaction — bleeding/hemorrhage into tissue, gaping, retraction of edges, clotting, inflammation, and healing. Post-mortem wound: no vital reaction — little/no bleeding, no gaping, no inflammation, edges do not retract.

How is age of a fetus/newborn estimated using Haase's rule?

For the first 5 lunar months, length in cm $=$ (months$)^2$; from the 6th to 10th month, length in cm $=$ months $\times 5$. E.g., at 4 months $\approx 16$ cm; at 8 months $\approx 40$ cm.

What is the definition and estimated volume for a fatal 'exsanguination' (hemorrhage)?

Exsanguination is death due to acute blood loss. Loss of about $\frac{1}{3}$ of blood volume (roughly $1.5\text{--}2\,\text{L}$ in an adult) rapidly can be fatal; total adult blood volume is about $5\,\text{L}$.

List the main types of asphyxial deaths.

Mechanical asphyxia: hanging, strangulation (ligature and manual/throttling), suffocation (smothering, choking, gagging), traumatic asphyxia, and drowning.

Differentiate the ligature mark of hanging from that of strangulation.

Hanging: oblique, non-continuous (incomplete), high up on neck above thyroid, directed towards the knot which is usually behind/side of ear. Strangulation: horizontal/transverse, continuous (complete) around neck, low down at or below thyroid cartilage level.

What is the classic autopsy triad/features suggesting death by drowning?

Fine, tenacious white/blood-tinged froth at mouth and nostrils, water and weeds in air passages/stomach, over-distended emphysematous 'ballooned' lungs, and (in fresh-water) hemodilution. Diatom test may support antemortem drowning.

Outline the medico-legal examination of a victim of alleged sexual assault (rape) — key evidence collected.

General examination for injuries/signs of struggle; examination of genitalia for injuries and hymenal status; collection of vaginal/oral/anal swabs for spermatozoa and DNA; pubic hair combings; clothing; blood/urine for drugs/alcohol; and documentation of consent, age, and mental state.

What is Forensic Psychiatry and define the McNaughton (M'Naghten) Rule.

Forensic Psychiatry applies psychiatry to legal issues (criminal responsibility, competency). The McNaughton Rule states a person is not criminally responsible if, at the time of the act, due to a defect of reason from disease of mind, they did not know the nature/quality of the act, or did not know it was wrong.

What is 'testamentary capacity'?

The mental ability of a person to make a valid will (testament). The testator must understand the nature of the act, the extent of their property, and recognize the persons who have claims upon them, and be free from delusion/undue influence.

State the importance of Forensic Odontology and Cheiloscopy.

Forensic Odontology uses dental records/features for identification of the dead (especially in mass disasters/burns) and analysis of bite marks. Cheiloscopy is the study of lip prints; like fingerprints, lip prints are unique to each individual and used for identification.

How is age estimated from teeth (eruption)? Give eruption times for temporary and permanent first molars.

Temporary (deciduous) teeth: eruption begins ~6 months, complete by ~2-2.5 years (20 teeth). Permanent teeth: first permanent molar erupts at ~6 years; permanent set (32 teeth) complete by ~17-25 years (third molar). Gustafson's method estimates age in adults from age changes in teeth.

Classify poisons based on their mode of action.

1) Corrosives (strong acids/alkalis); 2) Irritants (inorganic, organic, mechanical); 3) Neurotics/systemic (acting on CNS — cerebral, spinal, peripheral); 4) Cardiac poisons; 5) Asphyxiants; and miscellaneous. Also classified medico-legally as homicidal, suicidal, accidental, etc.

What is the general management of acute poisoning (broad principles)?

1) Stabilization (ABC — airway, breathing, circulation); 2) Prevent further absorption (decontamination — gastric lavage, activated charcoal); 3) Enhance elimination (forced diuresis, dialysis, urine alkalinization); 4) Administer specific antidote; 5) Supportive/symptomatic care.

Match these poisons with their specific antidotes: Organophosphates, Opioids, Paracetamol, Methanol, Cyanide.

Organophosphates → Atropine + Pralidoxime (oximes); Opioids → Naloxone; Paracetamol → N-acetylcysteine; Methanol → Ethanol/Fomepizole; Cyanide → Amyl nitrite + Sodium nitrite + Sodium thiosulfate (or hydroxocobalamin).

Describe the mechanism and classic clinical features (toxidrome) of organophosphate poisoning.

Organophosphates inhibit acetylcholinesterase, causing accumulation of acetylcholine. Muscarinic features: DUMBELS/SLUDGE (Diarrhea, Urination, Miosis/pinpoint pupils, Bronchorrhea/Bradycardia, Emesis, Lacrimation, Salivation); Nicotinic: fasciculations, weakness; CNS: seizures, coma. Diagnosis supported by low plasma/RBC cholinesterase.

Describe the mechanism of carbon monoxide poisoning and its clinical marker.

CO binds hemoglobin with ~$200\text{--}250$ times the affinity of oxygen, forming carboxyhemoglobin ($\ce{COHb}$), reducing oxygen-carrying capacity and shifting the oxygen dissociation curve to the left (tissue hypoxia). Sign: cherry-red skin/lividity; treated with $100\%$ oxygen or hyperbaric oxygen.

In forensic serology, differentiate presumptive from confirmatory tests for blood, and name the Kastle-Meyer test.

Presumptive tests (e.g., Kastle-Meyer/phenolphthalein test — turns pink; Benzidine, Luminol) indicate the possible presence of blood but are not specific. Confirmatory tests (e.g., Teichmann and Takayama crystal tests) and species identification (precipitin test) confirm it is human blood. DNA analysis gives individual identity.

What is the structure of DNA used in forensic profiling, and which technique/regions are analyzed?

DNA is a double helix of nucleotides (bases A-T and G-C paired). Forensic DNA profiling analyzes highly polymorphic Short Tandem Repeats (STRs) — repeating base sequences whose repeat number varies between individuals — amplified by PCR. Except for identical twins, each person's STR profile is unique, enabling identification and paternity testing.