Topic 6

Question 1

What can be examined to determine the time of death of a mammal?

Answer 1

Extent of decomposition

Stages of sucession

Forensic entomology

Body temperature

Degree of muscle contraction

Question 2

What is the human core body temperature?

Answer 2

36.2°C-37.6°C

Question 3

Why does body temperature drop when you die?

Answer 3

Heat-producing chemical reactions stop

Question 4

How is core body temperature measured?

Answer 4

Via the rectum or through an abdmonal stab using a long thermometer

Question 5

Why must a long thermometer be used to determine core body temperature?

Answer 5

An ordinary clinical thermometer is too short and has too small a temperature range

Question 6

Aside from a long thermometer, what may also be used to measure core body temperature?

Answer 6

An electronic temperature probe

Question 7

What must be noted when using core body temp to determine time of death?

Answer 7

Environmental conditions

They will affect how the body has cooled

Question 8

What type of graph does the cooling of the body follow?

Answer 8

A sigmoid curve

(S-shaped curve)

Question 9

After a person has died, how long does the inital temperature plateau last?

Answer 9

Between 30 and 60 mins

Question 10

What does the sigmoid curve graph of body temp after death assume?

Answer 10

That the person’s body temp was the normal 37°C at the time of death

Question 11

Why might someone’s core body temp not be the usual 37°C when they die?

Answer 11

They may have a fever or hypothermia, meaning their body temp will be higher/lower than normal

Question 12

Which part of the sigmoid curve of body temp is used to estimate time of death?

Answer 12

The near-linear part

(the middle bit)

Question 13

What does the near-linear part of the sigmoid curve show?

Answer 13

Temperature decline per hour

Question 14

What factors affect post-mortem cooling?

Answer 14

Body size

Body position

Clothing

Air movement

Humidity

Temp of surroundings

If body is in water

Question 15

Why do bodies immersed in water cool more rapidly than those in air?

Answer 15

Water is a better conductor than air

Question 16

What does rigor mortis mean?

Answer 16

Literally ‘stiffness of death’

It is the stiffening of muscles after death

Question 17

What happens to muscles after death?

Answer 17

They usually totally relax then stiffen

Question 18

What happens to joins during rigor mortis?

Answer 18

Become fixed in position - either flexed (bent) or extended (straight)

Question 19

What does the position of joints during rigor mortis depend upon?

Answer 19

The body position at the time of death

Question 20

Describe + explain the process of rigor mortis

Answer 20

1. After death, muscle cells become starved of oxygen and oxgen-dependant reactions stop
2. Respiration in cells becomes anaerobic + produces lactic acid
3. The pH of cells falls, inhibiting enzymes + thus anaerobic respiration
4. ATP needed for muscle contraction no longer made, so bonds between muscle proteins become fixed
5. Muscle proteins can no longer move over one another to shorten muscle fibre. Muscle + joints become fixed

Question 21

Which muscles stiffen first during rigor mortis?

Answer 21

Smaller muscles, then larger ones

Question 22

What causes rigor mortis to pass off?

Answer 22

Muscle tissue starts to break down

Question 23

Which muscle tissue breaks down first?

How does this relate the the order in which rigor mortis develops?

Answer 23

Smaller muscles break down first

This is the same order in which rigor mortis developed

Question 24

When will most human bodies have complete rigor mortis?

Answer 24

6-9 hours after death

Question 25

What can cause rigor mortis to set in more quickly?

Answer 25

If **enviromental temp** is **high** If the person has been **physically active** before death

Question 26

If a body is warm and not stiff, what is the approximate time since death?

Answer 26

Under 3 hours

Question 27

If a body is warm and stiff, what is the approximate time since death?

Answer 27

3-8 hours

Question 28

If a body is cold and stiff, what is the approximate time since death?

Answer 28

8-36 hours

Question 29

If the body is cold and not stiff, what is the approximate time since death?

Answer 29

36-48 hours

Question 30

What is autolysis?

Answer 30

The **destruction of cells** or tissues by their **own enzymes**, especially those released by **lysosomes** as well as the **digestive tract**

Question 31

Where do the bacteria that cause the body to decompose come from?

Answer 31

The **gut** + **gaseous exchange** system | (Some also from the surroundings)

Question 32

What is the first sign of decomposition?

Answer 32

Putrefaction

Question 33

What is putrefaction and what causes it?

Answer 33

**Greenish** discolouration to the **skin** of the **lower abdomen** Caused by the formation of **sulfhaemoglobin** in the blood

Question 34

Describe + explain the stages of decomposition

Answer 34

1. **Putrefaction** occurs first in skin of lower abdomen. Then **spreads** to rest of body. 2. Body then darkens to **reddish-green**, then turns **purple-black** colour. 3. **Gas/liquid blisters** may appear on **skin** 4. Body **swells** + becomes bloated due to formation of gases (hydrogen sulfide, methane, ammonia, hydrogen, and CO₂) by **bacteria** 5. As tissues **further decompose**, **gas released** + body **deflates** 6. When **fluid** associated with putrefaction **drains** away, soft tissues **shrink** + d**ecay rate of dry body reduced**.

Question 35

In average conditions, when will the discoloration of the abdominal wall occur?

Answer 35

36-72 hours post mortem

Question 36

In average conditions, when will gas formation as a result of decomposition occur?

Answer 36

About a week post mortem

Question 37

How does the temperature of the body deternine the rate of decompostion?

Answer 37

Occurs faster at warmer temps. If body temp remains above 26ºC, gas formation can occur within about 3 days

Question 38

What effect does enviromental temp have on the rate of decomposition?

Answer 38

Low temps slow decomposition Warm temps speed it up

Question 39

At what temps is the rate of decomposition highest?

Answer 39

21-38ºC

Question 40

What effect does intense heat have on the rate of decomposition and why?

Answer 40

**Delays the start** as intense heat **denatures** the enzymes involved in **autolysis**

Question 41

What effect do injuries to the body have on the rate of decomposition and why?

Answer 41

Aids/speeds up decomposition as allows the entry of bacteria