FORS-2106EL Final: FORS-2106 - Final Exam Review
27 Jun 2018
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Forensic Biology Final Exam Review
Day 1 - Entomology
-Forensic Entomology has 3 types, urban, stored-product, and medicolegal
entomology
-It is used to estimate PMI, post mortem interval, and we always assume minimum
PMI to ensure accuracy
-Why bugs?
-When a body decomposes, like when rigour mortis occurs, there will be an onset of
insect infestations
-Insects can detect decompositions from farther away then
humans
-Insects arrive at a corpse very quickly
-This is an accurate method
-Insect Development Rates
-Requires accurate ID of insects
-Must be correlated with environmental data like the
temperature of the body, ground, etc.
-There must be other info collected like the length of bugs
and maggots when collected
-ADH/ADD are one way of finding PMI with insect collections by looking at the size
and stage of an insect when it is collected, and comparing it to found data that will
tell us how long the body may have been in this environment, and if it had been
moved possibly
-There is a specific duration for each stage of life cycle at constant temperature
-This is mainly used for blowfly maggots
-Flies
-They are mainly found in ears, mouths, and mainly in warm moist areas
-Hairy Blow fly: very dark blue/green and metallic
-Screwworm Fly: dark blue with 3 darker stripes and red eyes
-Shiny bluebottle fly: thorax is grey, and has a shiny abdomen with brown eyes
-Black blow fly: looks black, or dark green/blue, and if you look behind his head (on
his shoulder) there is a spiracle with orange hair on it which is only found in this fly
-Flesh fly: pupil casings will be left on circus and will produce silk
-Cheese Skippers: they will come when the body starts to dry out, so its consistency
is moist and cheese like, and have maggots who will spring up
Day 2 - Entomology Con’t
-Beetle Larvae
-beetle larvae have pro-legs, which fly maggots do not have
-Scarab beetle larvae: curled up like
-Carrion beetle larvae: dark and larger with fringes around the body
-Rove beetle larvae: long with 2 long pro-legs at the end of the body
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-Skin beetle larvae: very hairy and smaller, and will feed off of dead skin flakes
-Beetles
-Carrion beetles: orange/yellow body parts and some may look like they’ve been
dusted with flour
-Burying beetles: have orange patches on elitra
-Skin beetles: look very hairy, can leave behind “silling string” which is waste
-Hairy Rove beetles: very big, with black and white stripes on it
-Clown beetles: look like black lady bugs
-Red-legged ham beetle: blue/turquoise and very small with red legs
-Scarab (dung) beetles: vey big or small and very robust, will eat animal waste
-Maggot Migration
-Maggots will migrate away from the body, each species is programmed to go a
certain distance and then borrow into the ground to pupae
-They will follow the sun which migrating, and when there is no sun they will go in
random directions
-The longer they remain pupae, the darker their colour becomes
-Insect Succession
-Analysis of all collected insects at a scene or on a corpse
-This is the other option when not using ADH/ADD
-Flies come first, then beetles
-Stages of Decay
-1) Fresh Stage
-begins when death occurs, ends when bloating begins
-2) Bloated Stage
-Begins when gases accumulate in the body and bloat occurs, with marbling of
the skin due to blood decomposing, and liquids leaving the body through the
orifices
-Odour will be strong
-Head will decompose first due to insects entering the body through the orifices
-3) Active Decay Stage
-Begins when the body is deflated from bloat
-Here the fresh skin will still be present, but it will have a wet appearance and
smell very strongly
-Reduced by 50% mass
-4) Advanced Decay Stage
-Most flesh will be gone, and weight loss will continue throughout this stage, while
carcass begins to dry out
-Odour will begin to fade
-5) Dry Stage
-Dry skin, bone, teeth, and cartilage with little to no odour
-6) Remains Stage
-Difficult to differentiate from dry stage
-Here only hair, bits of skin, and teeth remain and only incidental insects remain
-Necrophagous species: feed on the corpse
-Predators/parasite species: includes carrion feeding larvae and hunting adults
-Omnivore species: feed on corpse as well as other insects
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-Adventitious species: use corpse as it is in their environment
-Factors that affect finding PMI
-Temperature
-Greatest overall influence on insect activity and development
-low temp will lead to less activity, less egg laying and less development
-high temp will lead to high development, but it can exclude certain insects
-Moisture and Humidity
-Rain causes many flies to leave, or may drown insects
-Light/Shade
-Will have an effect on overall temperature
-Periodicity
-Affects insect activity, presence and timing
-Decreases flight activity due to sun setting earlier, therefore less fly time and less
egg laying
-Forensic entomology can also tell us about:
-Transportation of a body after death
-Disturbance of a body after death
-Presence and position of wounds
-Eggs will be deposited in natural body orifices or wounds
-Detection of drugs
-Can be used when the tissue is too decomposed to obtain organ samples
-Linking suspect/victim/scene
-Poaching
-Corpse Context
-Mummification
-Occurs in high temperatures with low humidity and will exclude insects
-Cremated Remains
-Flesh must be moist in order to attract insect activity, because once the tissue is
cooked, it is not habitable to insects
-Wrapped Remains
-Loose wrapping will be accessible and act as protection to insects
-Tight wrapping will be difficult for insects to get underneath it, so it will slow down
decomposition
Day 3 - History
-Forensic Science is a scientific process applied to the law, therefore we test different
possibilities/scenarios in cases/scenes
-Focusing on one single object in a case causes to investigative bias
-Taking evidence and trying to fit it into a scenario is inductive evidence and will lead
to bias
-We do not use the word “match”, instead we use “failed to exclude this individual”
when taking about our findings in order to try to reverse the bias
-It has its limits since test we use have limits of how accurate they are due to human
error in preforming the tests, writing reports, and testify, therefore there is room for
errors to occur
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Document Summary
Forensic entomology has 3 types, urban, stored-product, and medicolegal entomology. It is used to estimate pmi, post mortem interval, and we always assume minimum. When a body decomposes, like when rigour mortis occurs, there will be an onset of insect infestations. Insects can detect decompositions from farther away then humans. Insects arrive at a corpse very quickly. Must be correlated with environmental data like the temperature of the body, ground, etc. There must be other info collected like the length of bugs and maggots when collected. There is a speci c duration for each stage of life cycle at constant temperature. This is mainly used for blow y maggots. They are mainly found in ears, mouths, and mainly in warm moist areas. Hairy blow y: very dark blue/green and metallic. Screwworm fly: dark blue with 3 darker stripes and red eyes. Shiny bluebottle y: thorax is grey, and has a shiny abdomen with brown eyes.
