Lecture 10 - Forensic Entomology

Question 1

early changes after death - Algor mortis

Answer 1

up to 3 h: initial inhibition, 0.5°C per hour
up to 12 h: linear decrease, 1°C per hour
Drop in temperature after certain schedule and it is good to estimate the time of death if it is very soon after death, only up to 12 hours is this useful otherwise temperature goes up after this

Question 2

early changes after death - livor mortis

Answer 2

5-30 min: begin
2-20 h: blood pooling
12-48 h pushable
Blood spots, can see if the position of a corpse have changed because you always see the blood spots closest to the ground because blood travels towards gravity
Looks like a hematome
Blood spots when pushed can dissipate away and disappear i.e. pushable
Blood is pooling down towards the centre of the earth
Rigor mortis

Question 3

early changes after death - rigorous mortis

Answer 3

2-4 h: begin
6-12 h: complete
Duration: 48-72 h
2-10 d: release of contraction
Stiffness occurs in a particular way
Rigor mortis is usually complete after 12 hours and then it lasts some time after this
Temperature drops at the end because of release of contraction

Question 4

why does everything decay after death

Answer 4

because of chemical breakdown

Chemical breakdown is the reason why the temperature increases again and the reason for the stiffness to be released because the break down entering the microbiological activity because of the chemical breakdown

Question 5

what are the 3 big things that are undergoing chemical breakdown ?

Answer 5

proteins, carbohydrates, fats

Question 6

protein breakdown

Answer 6

Proteins —> peptides and amino acids —> sulphur, nitrogen and phosphor compounds, organic acids, aromatic compounds

Question 7

carbohydrate breakdown

Answer 7

Carbohydrate —> glucose —> alcohol, aldehydes, ketones, organic acids, ester and putrefaction

Question 8

fat breakdown

Answer 8

Fat —> glycerin and fatty acids —> un- and saturated fatty acid and oxygen compounds, nitrogen and phosphor

Question 9

fresh stage

Answer 9

Temperature drops, body get stiff, blood spots, start getting discolouration (greenish tinge of the stomach, blue)

Question 10

bloat stage

Answer 10

Gas production which bloats the entire body
Body hot again because of chemical breakdown
Gas pushes out body fluids through the natural body openings such as mouth and anus
Gas production is so much that it can cause skin rupture

Question 11

active decay stage

Answer 11

Most important stage for the forensic entomologists
Very strong in odour
Different stages within active decay, you have the Batric and Cheesy fermentation, cheesy fermentation smells strong like cheese and then have Black putrefaction (smells so bad you gag, body revolts, body reacts naturally to the odour) which makes the exposed parts of the body black in colour and there is a very strong smell of decay, large volume of body fluids
Main stage for most of the insects - will have lots of maggots on the body and activity going on on the body
Breakdown quite advanced and leaking into the ground
May get adipocere formation or if there is very high temperatures in the surroundings then you can get mummification (skin becomes very hard and dry

Question 12

advanced decay stage

Answer 12

Most of components are leaked out into the ground and the tissue becomes very dry if there is any left

Question 13

dry remains/skeletonised stage

Answer 13

skeleton, bone exposed

Question 14

succession of insects

Answer 14

During all the stages you have a succession of insects
Every insect species have their preferred stage of decomposition
There is a schedule of the order of which the insect species arrive and settle onto the corpse, they might feed on the corpse, they might lay eggs on the corpse, feed on other insects and come because they are predators or they mate on the corpse, this shows that every insect species have a specific reason to be inhabiting the corpse, some species use everything on the corpse such as feed, mate, rear etc

Question 15

types of insects of interest to forensic entomologists…

Answer 15

see poster

Question 16

how do the insects choose the right stage of decomposition?

Answer 16

every insect likes their specific decomposition stage
It is the smell that tells them
The nose of a fly are on the antenna
Foniculus* and the hairs on it are important, similar to human receptors in our noses, they are hair-like with little pores, they have binding proteins that bind the volatile chemicals that travel in through the pores and then you have protein transmitters or binding proteins that attach to the volatile chemicals and bind to a receptor and if it is something that the fly is attracted to then it the neuron would fire an electrical impulse i.e. action potential fired to tell the brain that it is something that it wants/interested in and wants to go lay its eggs their for example

Question 17

mechanism behind the smells and insect succession

Answer 17

It is not that a fly or beetle that has a favourite chemical it is the relation between the different chemicals that makes a particular smell more attractive to them

Question 18

Forensic entomology and locality of death

Answer 18

Locality of death - Insects present on the deceased body that are not prevalent to the crime scene can indicate that the victim was murdered elsewhere and was dumped at another location
You can tell if a corpse has been moved after death

Question 19

Forensic entomology and linking suspect to scene

Answer 19

if bugs can only be found in the same area as the dead body for example

Question 20

Forensic entomology and intoxication

Answer 20

!Change speed of larval development!
Can take a bunch of insects from the corpse and measure it all up and then can have a analysis
Shipments of illegal drugs often contain insect infestations - Track country of origin and the local area of cultivation

Question 21

Forensic entomology and wounds

Answer 21

Easy to get into wounds, because there is not soft tissue
Insects using go into the body opening first therefore normally mouth, nose and genitalia because they can easily get into the soft tissue
Sterile maggots can clean the necrotic/infected tissue off of wounds
Skin especially the hands are the last things eaten

Question 22

Forensic entomology and abuse and neglect

Answer 22

Abuse and neglect - especially children and elderly
Wounds are also an important sign of abuse
Self neglect, neglect may have open lesions even before death
Neglected children in the nappies would have larvae and even on their genitals

Question 23

Postmortem interval =

Answer 23

PMI = Minimal time of death

Question 24

PMI

Answer 24

After the insect has settled to the time the body has been found is known as the postmortem interval or the minimum time of death
Once you have the succession and once the insect lays eggs then you can investigate from the time the eggs develop to the time that the body was found
Collect all the entomological evidence you can

Question 25

Collecting insects for forensic investigations

Answer 25

Take all stages of life ***
Also collect from surroundings, under the body
Take temperature
Take soil sample - chemicals may have seeped into the soil
Surrounding is important because the insects are falling away when they want to pupate

Question 26

Maggots

Answer 26

Maggots are more precise for estimating time
If you collect all the maggots and identify the species and measure the size and say what stage they are
You can identify species by their hook or by their sphericles**which are their breathing openings, they look all different in different species
Measure the size and day what stage they are
Identify species

Question 27

Age of larvae

Answer 27

Retrospective calculation to estimate when eggs were laid

Question 28

Maggot life cycle

Answer 28

Timing of egg hatching is based on precise conditions and they only hatch when the optimal conditions are met, egg hatches into the 1st instar larvae in approximately a day and then grow into 2nd instar larvae
There are three instars of larvae before they pupate and then the adult will emerge and the cycle will start again, this timing is based on optimal conditions therefore temperature and humidity and other environmental conditions would affect the timing of this cycle

Question 29

Instar and breathing openings

Answer 29

Breathing openings are slit shaped, can count them and they correspond with the instars level so one slit is instar 1

Question 30

Two ways of estimating PMI

Answer 30

1- PAttern of succession: based on insect diversity at the time of body recovery
2- Age of the larvae: retrospective calculation to estimate when eggs were laid
- i.e. counting the sphericles

Question 31

Decomposition is …

Answer 31

1 succession of insect species
2 Insect development
+ Time, temperature, humidity, habitat, light, access —> all the different parameters that affect the cycle

Question 32

Lower temperature …

Answer 32

Lower temps slow down microbes & insects

- also decreases activity of the insects

Question 33

low humidity…

Answer 33

Low humidity dries corpse, mummifies

- body dries out and goes down the pathway of mummification

Question 34

Submerged vs on land

Answer 34

Submerged vs. on land

- body on land vs in water would decay in different ways and attract different insects

Question 35

open vs. interred vs. in shade

Answer 35

affects insect activity

Question 36

large wounds…

Answer 36

Large wounds lead to faster decomposition

More surface to act on for the insects

Question 37

scavengers …

Answer 37

Scavengers/vertebrate predators important too

- can affect the state of the corpse

Question 38

depth of burial ….

Answer 38

influences the bugs present and slows the rate of decomposition the further down you go

Question 39

tightly wrapped bodies…

Answer 39

Tightly wrapped bodies decompose slower

Question 40

heavy clothing….

Answer 40

Heavy clothing slows decomposition more than thinner clothing

Question 41

more fat…

Answer 41

More fat (higher water content, better heat retention) means faster decomposition

Question 42

insects on coke or meth or alcohol …

Answer 42

Insects on coke or meth burn through a body faster
Intoxication would speed up decomposition and also change the development of the maggots
Alcohol causes maggot growth to grow faster but they stay small in overall size
Instars is how you tell age in the early stages

Question 43

bodies with arsenic

Answer 43

Bodies with arsenic decompose slower

Question 44

Most important environmental factor is _________ and why

Answer 44

bugs have adapted to the local temperature
Cannot use bug data from other locations, need to look at their adaptations in the environment of the forensic examination you are doing
NZ needs to do experiments under different temperature circumstances for these locations
Hopefully use single sine otherwise can use database with excel that you can fed with all the circumstances/parameters you have such as temperature, humidity etc

Question 45

how many larvae stages are there of the blowfly

Answer 45

3 larvae stages

Question 46

succession of insects describes

Answer 46

Different insect species arrive over different time on a corpse and they all like different decomposition stages

Question 47

the blow fly life cycle has 6 parts…

Answer 47

the egg, 3 larval stages, the pupa, and adult