Forensic : post partum changes (80%)

What are postmortem changes?

Changes in the body after death due to cessation of vital functions.

List the main types of postmortem changes.

PM cooling, PM lividity (hypostasis), PM rigidity (rigor mortis), flaccidity (primary & secondary), putrefaction & substitutes (adipocere, mummification, maceration).

Define postmortem cooling (algor mortis).

Gradual decrease in body temperature after death due to stopped heat production while heat loss continues until body temperature equals surroundings.

Average rate of cooling in air during summer?

0.5-1 °C/hour.

Average rate of cooling in air during winter?

1-1.5 °C/hour.

Average rate of cooling in running water?

2-3 °C/hour.

Personal factors affecting postmortem cooling.

Age, obesity, cause of death.

How does age affect postmortem cooling?

Infants cool faster (large surface area, scant fat).

How does obesity affect postmortem cooling?

Slows cooling (insulating fat).

Two examples where postmortem cooling is slower.

Death with high fever, convulsions, acute infection.

Two examples where postmortem cooling is faster.

Death from hemorrhage, shock, wasting disease.

Medico-legal importance of postmortem cooling.

Estimate time since death, differentiate flaccidity stage, suggest cause of death.

Define postmortem lividity (hypostasis).

Bluish/violet discoloration of dependent body parts after death due to blood gravitation.

Mechanism of postmortem lividity.

Blood settles by gravity into dependent vessels after circulation stops; absent in pressure areas.

When does hypostasis begin to appear?

About 1 hour after death.

When is hypostasis fixed?

6-8 hours after death.

When does body movement cause complete shift of hypostasis?

Within 2 hours after death.

Effect of changing position between 2-8 hours after death (hypostasis).

Incomplete new hypostasis with original site still visible.

Effect of changing position after 8 hours (hypostasis).

No change in hypostasis site (blood clotted).

Medico-legal importance of hypostasis.

Sure sign of death, estimate time since death, show body position at/after death, suggest cause of death.

Hypostasis color in normal death.

Violet.

Hypostasis color in asphyxia.

Deep blue.

Hypostasis color in CO poisoning, cyanide poisoning, or cold deaths.

Bright red (cherry red).

Hypostasis color in hemorrhage or vagal inhibition.

Pale.

Hypostasis color in methemoglobinemia.

Brown.

Define rigor mortis.

Postmortem progressive rigidity of muscles after primary flaccidity and before secondary flaccidity.

Mechanism of rigor mortis.

ATP depletion → actin-myosin fixation → muscle stiffness.

When does rigor mortis first appear and where?

\~2 hours after death in small facial muscles.

When is rigor mortis generalized?

By 12 hours after death.

Order of disappearance of rigor mortis.

Same order as appearance — face first, then downwards.

Cause of rapid rigor mortis.

Death from convulsions (ATP exhaustion).

Three factors affecting rigor mortis.

Muscular build, temperature, cause of death.

Define cadaveric spasm.

Instantaneous postmortem rigidity of a group of voluntary muscles at moment of death due to nervous excitement.

Onset difference between rigor mortis and cadaveric spasm.

Rigor mortis is gradual (\~2 hrs); cadaveric spasm is immediate.

Medico-legal importance of cadaveric spasm.

May hold clues to assailant, support suicide diagnosis, indicate drowning if grasping aquatic material.

Define primary flaccidity.

Immediate muscle relaxation after death; muscles respond to stimuli.

Define secondary flaccidity.

Flaccidity after rigor mortis due to autolysis; no muscle response to stimuli.

Time difference between primary and secondary flaccidity.

Primary: immediate; Secondary: \~18-25 hrs after death.

Define putrefaction.

Postmortem breakdown of soft tissues until only bones remain.

Processes causing putrefaction.

Autolysis (enzymes) and bacterial action (aerobic/anaerobic).

Earliest visible sign of putrefaction and time.

Green discoloration of right iliac fossa — 1 day in summer, 2 days in winter.

What is arborization in putrefaction?

Marbling of skin due to hemolysis and hydrogen sulfide reaction in superficial veins.

Rule of thumb for decomposition in air, water, ground.

1 week air = 2 weeks water = 8 weeks ground (same temperature).

Factors accelerating putrefaction.

Warm temp (25-40°C), obesity, humidity, ventilation, certain causes of death (fever, infection).

Factors delaying putrefaction.

Cold, burial, low body fat, wasting disease, hemorrhage, dehydration, metallic poisoning.

Define adipocere.

Waxy, greasy, yellow-white postmortem fat transformation in bodies submerged in water.

Time for adipocere to appear and complete.

Appears 3-4 weeks; completes \~6 months.

Define mummification.

Drying and preservation of body in hot dry environments.

Time for mummification to start and complete.

Starts \~1 week (exposed areas); completes in 3-12 months.

Define maceration (fetal).

Aseptic autolysis of fetus in utero after death; flaccid, edematous, brown, with possible Spalding's sign.

Methods to estimate time since death (5 main).

Cooling rate, hypostasis extent, muscle state, putrefaction stage, insect activity.

Bulk of meal leaves stomach in how long?

\~2 hours.

Complete stomach emptying time.

\~6 hours after last meal.

Intraocular pressure change after death.

Drops from \~25 mmHg to 12 mmHg at death; zero in 2-3 hrs.