The estimation of Time Since Death and the Post Mortem Interval (week 1, lesson 1/1)

Thanatos-Diagnosis

A thanatos-diagnosis refers to the determination of time since death—also known as the post-mortem interval (PMI).

Estimating the exact time of death with hourly precision is not scientifically reliable or achievable.

Processes from the corpse to the bones

1. Decay

2. Disruptive phenomena - he physical and chemical breakdown of the body caused by both internal and external factors.

> Abiotic

-> immediate - conditions acting on the body shortly after death (temperature, humidity, exposure to air/water/soil, body position and clothing).

-> consecutive - come into play after decomposition has started (sunlight, rain or flooding, pH of the soil or water).

> Transformative - internal and microbial actions that chemically and physically transform the body

-> autolysis - The breakdown of cells by their own enzymes

-> auto-digestion - self-degradation of tissues

-> putrefaction - bacterial activity leading to liquefaction of tissues, marbling, discoloration

What's the immediate abiotic phenomena

The non-living environmental factors that affect the body shortly after death, often before or during the very early stages of decomposition.

Necessary for a statement of death

Criteria for the statement of death

- absence of motility and consciousness

- no breathing

- no heartbeat and arterial pulse

- absence of pupillary and corneal light

reflexes

What's the consecutive abiotic phenomena

These are ongoing or delayed environmental influences that impact the later stages of decomposition and can affect how, how fast, and to what extent a body breaks down over time.

- progressive cooling (algor mortis)

- hypostasis (livor mortis)

- muscle stiffness (rigor mortis)

- dehydration of the body

- modification of the eyeball

- gradual disappearance of neuromuscular

excitability

- acidification of fluids and tissue reaction

Algor mortis - The Cooling/warming of the Body

Algor mortis is the post-mortem cooling for warming of the body until it reaches equilibrium with the temperature of the surrounding environment.

Suffers from a variety of limitations

- Assumption of 37°C as temperature at death

- Influenced by the physical and physiological conditions of the subject before death

- Affected by the environment and clothing

Livor mortis

Livor mortis is the settling of blood in veins/capillaries of the dependent (lowest) parts of the body after death due to gravity. It causes visible purple-red discoloration of the skin in those areas, often called lividity or hypostasis.

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Distinguished from bruises because is not due to blood outflowing from broken vessels. Could be associated to fluid accumulation (oedema) and blisters on the skin due to plasma settling.

What is Shifting in Livor Mortis?

Shifting refers to the ability of unfixed lividity (the discoloration from livor mortis) to relocate to a new position if the body is moved before the blood becomes permanently settled.

• Appearance 20/120 minutes after death• Total shifting 4/5hrs• Partial shifting 6/8hrs• Fixed 10/12hrs• Disappearance 48/72hrs

What's a pressure pallor

Pressure pallor (also called contact pallor or contact flattening) refers to the pale areas of skin that do not show lividity because they were under pressure at the time blood was settling after death.

How can livor mortis be a good indication of if a body has been moved

Alteration of the body position can be detected by a non consistent hypostasis' pattern

What's cherry red hypostasis

Cherry red hypostasis refers to an unusually bright red or pink coloration in the lividity (post-mortem discoloration) of the body, rather than the typical bluish-purple seen in most deaths.

It's typically caused by abnormal levels of oxygen or oxygen-like compounds in the blood at the time of death (carbon monoxide poisoning). These conditions bind hemoglobin in a way that gives blood a bright red color—even after death.

Rigor Mortis

Rigor mortis refers to the stiffening of muscles after death due to biochemical changes in muscle tissue, which leads cadaveric rigidity (rigid, stiff body).

The biochemical changes:

- post-mortem rise in the intracellular concentration of calcium ions

- disappearance of the ATP from muscles whichpermanently links myosin and actin filamentstogether

• Immediate muscle relaxation (sphincters loosening)

• Initial stiffening after 2-4hrs

• Nysten's law (2-3 hrs mandible- 7-12 hrs lower limb)

• Complete 8-12hrs

• Disappearance after 36hrs

• Cutis anserina (goose bumps) due to arrector pilimuscles stiffening

How can rigor mortis be a good indication of if a body has been moved

If rigor mortis is inconsistent with the position at the crime scene

What's a cadaveric spasm

Instantaneous appearance of rigor mortis subsequent to violent or heavy exercise

Eye modifications

• Consequences of post-mortem drying

• Discolouration of the sclera/pupil (tache noire) or entire eyeball, which could turn red to brown-black

• Chemical changes in the potassium ionconcentration in the vitreous humour

Gastric emptying and contents

The stomach takes 3-4 hours to empty and the small intestine 2-7 hours.

What's the transformative phenomena

Transformative phenomena are post-mortem biological processes that lead to the breakdown and transformation of body tissues. They occur naturally from within the body (endogenous) and can be influenced by external factors (exogenous) like temperature, humidity, and insect activity.

Autolysis

Self-destruction of cell populations by lysosomal proteolytic enzymes that are released after the death of the cell

Auto-digestion

Lytic enzymes from digestive juices can perforate the stomach wall starting the digestion of internal organs

Putrefaction

Biological active phenomenon which involves enzymes produced by bacteria and germs, both external and regular guests of the human intestine(e.g. Clostridium perfringens, butyric, tetanii).

Putrefaction Stages

1. Chromatic

2. Bloating

3. Black putrefaction

4. Dry decay

Chromatic stage

This is greenish discolouration of the lower right quadrant of the abdomen and emphasis on the subcutaneous venous branching pattern (marbling) due to haemolysis.

- Discolouration pale green to green-black.

- Takes 20-25 hours in summer compared to 2 days in winter.

Bloating

Bloating areas:

- Facial features are swollen, the eyes bulge, and the tongue protrudes between lips

- Blistering of the skin and epidermolysis

- Detachment of the scalp and hair

This is because gases produced fill all the cavities (e.g. scrotum) and purge fluids are forcefully expelled from the orifices.

- Takes 3-6 days in summer compared to 3-6 weeks in winter.

Black putrefaction

This is collapsing of the body where the brown-black colour of the corpse dissolves into brown liquid.

- Takes 15 days in summer compared to 1-2 months in winter.

Dry decay

This is skeletonisation. Tendons and ligaments could be retained after the tissues loss.

- Takes 2 months in summer compared to 8-10 months in winter & if they were buried then 2-5 years.

Factors that can affect decomposition speed

Conservative processes - adipocere and mummification

Speeding processes - insect activity

Adipocere

This is the breakdown of body lipids which produce a fatty greyish substance that will inhibit further decomposition. Causes skin maceration.

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- Needs wet environment

- Complete after 6-12 months

- Commonly seen in stillbirths (foetus kept in amniotic fluid after death) & drowning victims

What's skin maceration

The softening, swelling, and breakdown of the skin due to prolonged exposure to moisture—without active bacterial decomposition (initially).

What's face horripilation

The appearance of goosebumps (piloerection) on the facial skin or scalp, particularly visible after death. Especially in violent or traumatic deaths (e.g., drowning, electrocution, or extreme stress), nerve signals or muscle reactions may persist briefly or activate during the dying process, causing the small erector pili muscles in the skin to contract. So hairs stand up and skin appears bumpy.

Early, advanced and complete adipocere

1. Early - 1-4 weeks -

Greyish-white patches, soft and greasy -

Indicates moist environment, decomposition slowing

2. Advanced - 1-3 months - Firm, waxy, larger areas affected - Suggests intermediate PMI, tissue preservation

3. Complete - Months to years - Full waxy coverage, firm and dry, preserved form - May preserve ID features, long PMI, delayed decay

Mummification

This is dehydratation of tissues due to extreme hot/cold conditions that will inhibit further decomposition.

- Superficial 4-8 weeks; complete 6-12 months

Insect and animal activity

Insects and scavengers can accelerate every phase by physically breaking down the body and spreading bacteria.

Flies and maggots eat soft tissue rapidly & increase bacterial spread.

Scavengers tear open body cavities, eat tissue & displace body parts.

Forensic Entomology

The study of insects to determine such matters as a person's time of death and their relation to a criminal investigation.