Time of Death

Question 1

What is a sigmoid curve?

Answer 1

• A sigmoid curve is a curve having the shape of a stretched ‘S’

Question 2

What is known as rigor mortis?

Answer 2

• After death, muscles usually totally relax and then stiffen, this stiffening is known as rigor mortis

Question 3

What is decomposition?

Answer 3

• Decomposition is the process in which after death, tissues start to break down due to the action of enzymes

Question 4

What is autolysis?

Answer 4

• This is when the body’s own enzymes, from the digestive tract and from lysosomes, break down cells

Question 5

When using body temperature to determine the time of death, what are the factors that affect this method?

Answer 5

• body size
• body position
• clothing
• air movement
• humidity
• temperature of surroundings

Question 6

When using rigor mortis to determine the time of death, what are the factors that affect this method?

Answer 6

• temperature of surroundings
• if person was physically active before death

Question 7

When using stage of decomposition to determine the time of death, what are the factors that affect this method?

Answer 7

• temperature of climate
• temperature of the body

Question 8

What is the range of normal human core temperature?

Answer 8

• human core temperature is normally in the range of 36.2 to 37.6 C

Question 9

How is core body temp usually measured? What is needed? What must be noted?

Answer 9

• core body temp is measured vie rectum/ abdominal stab
• a long thermometer is needed (small one is too short and too small temp range), electronic probe can also be used
• environmental conditions must be noted

Question 10

What factors could affect post-mortem cooling?

Answer 10

• body position
• clothing
• temperature of surroundings
• body size
• humidity/ water
• air movement

Question 11

What would a hot environmental temp mean for rigor mortis?

Answer 11

• hot environmental temp means rigor mortis sets in quicker and for shorter period

Question 12

What is the approximate time of death for a body that is warm but not stiff?

Answer 12

• less than 3 hours

Question 13

What is the approximate time of death for a body that is warm but stiff?

Answer 13

• 3-8 hours

Question 14

What is the approximate time of death for a body that is cold but stiff?

Answer 14

• 8-36 hours

Question 15

What is the approximate time of death for a body that is cold but not stiff?

Answer 15

• 36-48 hours

Question 16

What is the sequence of events in rigor mortis?

Answer 16

1) Initially body continues to respire anaerobically but a build up of lactic acid denatures respiratory enzymes
2) So no ATP is produced
3) No ATP to pump Ca2+ out of the sarcomere so binding sites for muscle proteins remain exposed and cross bridges are formed (= muscle contraction)
4) No ATP to break ‘cross-bridges’ that form in muscle contraction

Question 17

What affect will a well-heated room have on decomposition?

Answer 17

• a well-heated room speeds up decomposition; raises the body temperature so rate of enzyme action increases

Question 18

What affect will injuries to the body surface have on decomposition?

Answer 18

• injuries to the body surface speeds up decomposition; allows entry of bacteria

Question 19

What affect will intense heat have on decomposition?

Answer 19

• intense heat slows down decomposition; destroys the bacteria and denatures enzymes involved in decomposition

Question 20

What are the following sequence of events that occur after death in rigor mortis? (textbook edition)

Answer 20

1) After death, muscle cells become starved of oxygen and oxygen-dependent reactions stop
2) respiration in the cells becomes anaerobic and produces lactic acid
3) the pH of the cells falls, inhibiting enzymes and thus inhibiting anaerobic respiration
4) the ATP needed for muscle contraction is no longer produced. As a result, bonds between the muscle proteins become fixed
5) the proteins can no longer move over one another to shorten the muscle, fixing the muscle and joints.

Question 21

What is the larva?

Answer 21

• larva is the stage of development of many animals
• it is a distinctive juvenile form many animals undergo before metamorphosis into their next life stage

Question 22

What are the three stages of larva called?

Answer 22

the three stages of larva are called instars

Question 23

What is a pupa?

Answer 23

• an insect in its inactive, immature form between larva and an adult
• (life stage in the development of insects exhibiting complete metamorphosis that occurs between the larval and adult stages (imago))

Question 24

What is forensic entomology the analysis of? What is it often used for?

Answer 24

• forensic entomology is the analysis of the insects found on decomposing tissue
• which is often used to determine the time of death

Question 25

What is the definition of a maggot?

Answer 25

• a soft-bodied, legless larva of a fly/ insect that is found in decaying matter

Question 26

What is the difference between the feeding and the post-feeding stages

Question 27

What does ambient temperature refer to?

Answer 27

• ambient temperature refers to the current air temperature in the surrounding environment

Question 28

What are some observations that can be recorded on a dead corpse to help determine the time of death?

Answer 28

extent of:
- decomposition
- colour
- smell
- bloating
- degree of rigor mortis/ muscle contraction

Question 29

What does succession refer to?

Answer 29

• succession refers to the change in the types of organisms found in a habitat over time

Question 30

What does succession on corpses refer to? What do forensic entomologists do with this information?

Answer 30

• in succession of corpses, as one group of organisms feed on a decomposing body, conditions change in such a way that it becomes attractive to another group of organisms
• as the corpse continues to change, it attracts different organisms that feed on it until only the skeleton remains
• forensic entomologists use the predictable sequence of organisms that feed on a decomposing body to determine the time of death