Determining the time of death Flashcards Preview

Topic 6 > Determining the time of death > Flashcards

Flashcards in Determining the time of death Deck (14):
1

Describe body temperature

Normal range is 36.2-37.6C
Used up to 24hrs after death
Measured via the rectum or abdominal stab into the liver
Cooling of the body follows a sigmoid curve
Factors affect accuracy:
Surface area, temperature, clothing, size and air movement

2

Describe rigor mortis

After death muscles usually totally relax and then stiffen
Joints become fixed during RM and position depends on body position at time of death
Small muscles go first
Hot temp means RM sets in quicker and shorter period

3

Describe the chemistry of rigor mortis

Muscles become starved of oxygen and respiration becomes anaerobic
Lactic acid denatures respiratory enzymes so no ATP is produced
no ATP to pump calcium out of sarcomere so binding sites remain exposed and cross bridges form
no ATP to break cross bridges that form in muscle contraction

4

Describe the first sign of decomposition

Putrefaction: greenish discolouration of skin of lower abdomen due to autolysis (tissue brokedn down by enzymes)
36-71 hours

5

Describe the second sign of decomposition

Discolouration spreads from redish green to purple
Gas or liquid blisters appear on skin due to build up of respiration gases from bacteria, corpse swells in a week

6

Describe the third sign of decomposition

Gas released and body deflated, fluid from 1st sign drains away, soft tissue shrinks
Factors: temp, injuries, location

7

Why would a well heated room speed up decomposition?

enzymes have more kinetic energy so more enzyme-substrate complexes formed
Bacteria multiply and more rapidly

8

Why would intense heat slow down decomposition?

Enzymes denature so bonds between R groups broken
Enzymes lose their specific shape so active site changes shape

9

What to look for to estimate time of death?

Length of maggot
Time taken to pupate
Temperature and species present

10

What is a maggot

Soft bodied legless larva found in decaying matter

11

Define forensic entomology

Use of insects that inhabit decomposing remains to solve crime

12

How do you measure the age of a maggot

Find length of maggot and temperature
Draw lines from temp to length

13

Describe estimating time of death based on egg hatching

If development is unclear, its allowed to pupate
Subtract hatching time normally from date of pupation
May be an underestimate as theres no knowing of how long it took for flies to find the body and lay eggs

14

Describe succession on a corpse

One species feed on decomposing body changing conditions to make it suitable for another species
Produces competition
Eggs laid in wounds or opening to the body
Species used to estimate time since death