The tickle of curiosity. The gasp of discovery. Fingers running across the keyboard.

The tickle of curiosity. The gasp of discovery. Fingers running across a keyboard

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Thursday, December 12, 2013

Forensic Entomology: Something's Bugging Me About the Murder Scene

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Description: Calliphora vicina. Blow-flies (al...
. (Photo credit: Wikipedia)
WARNING: The photos and videos contained in this blog may be considered graphic in nature. Please 
consider your tolerance before viewing.



Your character arrives at the crime scene ready to put her full professionalism into play and solve the crime.
Uh oh! They've found a body. Your heroine calls in the coroner  because it's required by law. But very quickly, your heroine realizes from the state of the remains that the body has been decomposing for over 72 hours. So she makes two more calls:
Blow-flies
Blow-flies (Photo credit: Wikipedia)
* the forensic anthropologist to process the remains.
* A forensic entomologist to process the bugs.

- Blog Link to Crime Scene 101
Blog Link Coroner/Death
   Investigator
Blog Link Algor, Livor, and
   Rigor Mortis
Blog Link Forensic
   Anthropologist

* In the first 72 hours there are more precise ways to
   determine time of death than by using insect evidence.
* After 72 hours insect evidence is the most accurate
   and possibly the only way to determine time of death.


A forensic entomologist - deals with any bugs that would show up in the court of law. 

Video Quick Study (2:42) a forensic entomologist talks about his job.


Sometimes, because of access, distance, or budgets, getting a forensic entomologist to the crime scene is not possible. A CSI can gather the evidence.

A Typical Crime Scene Kit
A Typical Crime Scene Kit (Photo credit: Wikipedia)
Video Quick Study (1:36)  Review of a field forensic entomology kit.
* Different species should be kept separate
* Insects collected from different body parts should be kept
   separate.
* Maggot clusters should be documented, photographed, and
   temperatures obtained.
* The specimens should be labelled with:
   - date and time
   - name of the collector
   - stage of insect development at time of the collection
* When the bugs are collected your character will want to have 2
    vials:

- Sample One - contains alcohol (the bugs die) this shows:
   1. what stage of development the bugs were in when they were
       collected
   2. helps the emtomologist to define the approximate time of death
   3. can be used  in court as evidence.

- Sample Two - keeps the specimens alive. Add a dampened paper
   towel and cover with dry paper towel held on with a rubber band.
   This allows the entomologist to incubate the insects in their lab 
   and determine a  more specific time line.
  

Other data that will help a forensic entomologist make sound scientific inferences in the laboratory include:

* Habitat: ex desert, vegetative, meadow, woods
Ruler in use at a mock crime scene
Ruler in use at a mock crime scene (Photo credit: Wikipedia)
* Soil samples
* Weather at the time of collection 
    including: shady? sunny? 
    raining? temperature?
* Vegetation in the area
* Death site including elevation
   and map coordinates
* The state of the remains
* Were the remains buried? How
   deeply?
* What clothes or wrapping
    surround the remains?
* Anything else that the CSI thinks
   might help inform the process.

Photography is VERY helpful

Video LONG Study (15:11) Prt 1, Canadian entomologist discussing crime.
Video LONG Study (6:42) Prt 2


Okay, let's get to the bugs themselves

English: Describing the relationships between ...
English: Describing the relationships between carrion insect trophic specializations and decomposing remains, adapted and simplified from K.G.V. Smith, A Manual of Forensic Entomology, 1986 (Photo credit: Wikipedia)
Some terms: 
* Nacrophagous Species - feed on dead things.
* Omniverous Species - will eat most anything
* Predators - come to eat the necrophagous and omnivorous
   species of insects
* Parasites - are brought in by the other insects
* Adventive species - can be particularly informative. If the
   entomologist finds sub-types of species whose habitats are in a 
   different geographical location, they can determine that the body
   had been moved.
    Video Quick Study (1:49) Entomologist looks at the air filter on       a car to determine if the suspect drove  across the United States 
    to commit a murder.


The first on the scene is the blow fly.


English: Sarcophaga (Liopygia) ruficornis fles...
English: Sarcophaga (Liopygia) ruficornis flesh-fly mating.  (Photo credit: Wikipedia)

* Blow flies can smell death and
   can be there in mere moments.
* They lay their eggs immediately
   in openings. This can
   mean: mouth, eyes, nose, ears, 
   anus and vagina, and
   importantly, wounds. 

Now why is that important? If the remains have decayed past the point of recognition, finding the maggot mounds can help identify where that person might have been injured.

Why might this be bad? - When the eggs hatch and the larvae
starts to eat they are:
* destroying the facial features of the deceased, making
   identification more difficult
* can damage the wound margins making forensic wound study
   difficult.

Quick review of your Biology 101 class - here are the stages of blow fly life:
1. egg is laid - NOTE: flies
    are only active during
    daylight. If the person dies
   at night, the first eggs
   won't be laid until
    morning.

Video Quick Study (2:11) fly laying eggs on deceased bird.

2. maggots come out and start to consume the corpse
3. larvae grows and eats
4. The larvae are full and stop eating. They migrate away from the
    body to pupate (hard cocoon-like stage while their DNA
    rearranges them into a fly). They like to do this in cool
    conditions. They will crawl under rugs, into the clothing
    especially seams, pockets, and cuffs, or if this isn't available -
    earth.
5. Pupae - because they change color can be aged to a matter of
    hours.
6. Emerging as a fly

* This whole cycle takes about 2 weeks depending on:
- Species 
- Weather (warmer temperatures creates more activity)
- Quality of the food
- Oxygen levels
- Day length/season

Video Quick Study (6:52) Close up video of blow fly life cycle.

Video Quick Study - Murder case in Hawaii where the body was wrapped in blankets.
.

* If a body is discovered in the first month postmortem interval, PMI, entomologists can be accurate to
   within a day.
* After first generation of blowflies has developed, the
   entomologist looks at the succession of insects. This is
   used when the corpse is dead for a month or more. The wave of
   insects overlaps.



Insect Arrival Comes in Waves

English: Blow flies (chrysomya megacephala) on...
English: Blow flies  (Photo credit: Wikipedia)

1. Flies - attracted by the
   decomposition odor arrive
    immediately. They like fresh
    bodies because of water
    content.






Oiceoptoma thoracicum (Silphidae)
Oiceoptoma thoracicum (Silphidae) (Photo credit: gbohne)
2. Carrion Beetles - Arrive in a few days
    during putrefaction stage
    body liquids are starting to expel from
    the corpse, lot's of odor
    more and more insect activity. (flies
    and wasps will also be
    there)






Closer view of a carpet beetle
Closer view of a carpet beetle
(Photo credit: Dendroica cerulea)
3. Carpet Beetles - come during the dry stage - skin is hardening
    an becoming leathery, some bone is starting to protrude out of
    decomposition. The carpet beetles come to eat the hair, skin
    and bone. Coffin flies, cockroaches and flies are there as well.

Video Quick Study (8:53) a forensic teacher takes you through the insect stages.
Video Quick Study (7:31) video of an animals decomposition, focusing on insect activity

Interestingly, bugs:
* can carry corpses dna
* can ingest drugs
Video Quick Study (2:45) Student's on site
Video Quick Study (6:38) Student forensic entomologists.

* Bugs can only tell the entomologist how long the body has been
   available to the bugs. So for example, if the body was in a deep
   freezer and then removed  and put in the woods, the timing would
   be based on when the body was available to the bugs.
* In much of Canada and northern United States, cold winter
   months mean entomologists cannot use insects to determine time
   of death.
* In the summer, a body can decompose down to bones in as little
   as two weeks.
* Decomposition in water - standard insects don't apply but other
   organisms do.





CRIME SCENE DO NOT CROSS / @CSI?cafe
CRIME SCENE DO NOT CROSS / @CSI?cafe (Photo credit: Wikipedia)



CASES


Collecting insects at a mock crime scene
 (Photo credit: Wikipedia)
1. Video Quick Study (3:58) Prt 1
   Video Quick Study (3:32) Prt 2

2. Video Quick Study (1:42) Entomologist testifying
     in Casey Anthony Trial

3. Video Quick Study (1:49) Entomologist looks at
    the air filter on a car to determine if the suspect
    drove across the United States to commit a
    murder.




See how this article influenced my plot lines in my novella MINE and my novel CHAOS IS COME AGAIN.





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3 comments:

  1. This is such good information that I'm saving it. Thank you for posting it.

    ReplyDelete
  2. BRAVO, VERY GOOD INFORMATION.

    ReplyDelete
  3. This is awesome! Thank you for sharing again on Twitter!

    ReplyDelete