Topic 6: Estimating time of death III (forensic entomology)

What does a post mortem usually refer to?

Autopsy- examination of a body after death

What are the stages in a life cycle for a blow fly?

• Egg

• Larva (first instar)

• Larva (second instar)

• Larva (third instar)

• Pupa

• Adult blow fly

How can you use forensic entomyology to estimate TOD?

Can look at which stages of the lifecycle there are present of the insects present to estimate TOD

How long does it take for the blow fly egg to hatch?

24 hours

What happens to he larva between the first and second instar as well as the second and third instar?

The larva moults

What is the process called in which the larva becomes a pupa?

Pupation

How can external factors affect the time it takes for bow flies to initially colonise a body?

• If extreme wind conditions → odour gets blown away (blow flies won’t be able to locate the dead body)

• Temperature → higher warmth → more kinetic energy → more collisions → higher metabolic rate

• Whether body is outdoors or indoors (if body is outdoors, the blow flies can colonise the body more readily)

• Whether body is wrapped or not (can conceal body odour as well as making it harder for blow flies to colonise the body as there is a physical barrier)

What processes affect the time taken for a blow fly life cycle to be completed?

• Temperature (warmer temp → increased metabolic rate)

• Presence of drugs (dependant on drugs → can increase or decrease rate)

• Food availability (not really on syllabus)

• Oxygen availability (blow fly need oxygen to respire)

Describe succession on a body post-mortem, also explain why conditions are favourable and what species leave

When using stage of succession to determine time of death, what do you need to take into account?

When using stage of succession to determine time of death, environment variables need to be taken into account

How does diversity of the decomposition community change over time?

Increases over time and then decreases over time.