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What Is Forensic Entomology?


'Who saw him die?'
'I', said the fly
'With my little eye,
I saw him die.' — Anonymous


Definition of Forensic Entomology

Forensic entomology is the study of insects associated with a human corpse in order to determine elapsed time since death. Insects and their remains collected at a crime scene are often used as evidence in a variety of court cases including but not limited to murder. The primary purpose of a forensic entomologist is to determine the time which has elapsed since the murder of an individual. However, abuse cases and some civil cases have also employed forensic entomologists when insect activity is implied in evidence.

Forensic entomologists, typically employed by academic institutions not law enforcement agencies, may also be called to provide evidence of the following:

  • that the body had been moved to a secondary site either by animals or the killer.
  • that the body was disturbed at some time after death.
  • insect activity may determine the presence and position of wounds
  • analysis of insects found on a body may determine the presence of drugs
  • insects or remains present on a suspect or suspects vehicle may place the suspect at the scene of the crime
  • insect evidence may be used in civil cases
  • child or senior abuse cases may benefit if insects have colonized wounds

In the midst of all this decay, death calls in reinforcements. — Heather Pringle


History of Forensic Entomology

  • Its first use was reported in 1235AD China.
  • During the Middle Ages, sculptors, painters and poets closely observed the decomposition of bodies by insect action and depicted their observations through their works.
  • It was used sporatically in the 19th C.
  • It was used sporatically in the early 20th C, playing a part in some major cases.
  • In France and Germany, during the 18 and 1900s mass exhumations provided evidence that maggots played a major role in the decomposition of human cadavers.
  • From May 1899 to September 1900, medical examiner Eduard Ritter von Niezabitowski placed aborted fetuses, cat, fox, rat, mole and calf carcasses on a windowsill and in a nearby vegetable garden providing proof that human cadavers share similar insect succession with both vertebrate and invertebrate creatures.
  • In the 1920s, species lists and monographs were published of forensically important species of insects.
  • In 1996, the American Board of Forensic Entomology (a certification board for forensic entomologists) was formed.
: A flesh fly, probably Sarcophaga nodosa feeding on decaying flesh.

: A flesh fly, probably Sarcophaga nodosa feeding on decaying flesh.

Criminal Cases In Which Forensic Entomology Played A Major Role

  • The first documented forensic entomology case was recorded by the Chinese death investigator Sung Tzu in Hsi yüan chi lu where a stabbing at a rice field was determined to be by a sickle which attracted blow flies due to traces of blood. The owner of the sickle confessed to the murder.
  • The first modern case where PMI (post mortem interval) was used was in the case of an infant found entombed in the walls of a house. The French doctor Bergeret provided evidence on Blow flies and larvae associated with the corpse and although his estimation of life cycle data was not accurate, he made an attempt based on knowledge at the time in estimating time since death of the infant and a determination of the killer was made based partially on that evidence.
  • The murder of the wife and maid of Dr. Buck Ruxton who were discovered in a ravine in Dumfriesshire, Scotland in 1935 was closed due to insect evidence. The bodies contained blowfly larvae which provided a vital clue as to the time of the murders and resulted in the conviction of Dr. Ruxton.

Major Insect Families of Interest to Forensic Entomologists

Major Fly FamiliesMajor Beetle Families

Family Calliphoridae: Blow flies

Family Silphidae: Carrion beetles

Family Sarchophagidae: Flesh flies

Family Dermestidae: Skin, Leather, Hide Carpet and Larder beetles

Family Muscidae: Muscid flies

Family Staphylinidae: Rove beetles

Family Piophilidae: Skipper flies

Familiy Histeridae: Clown beetles

Family Scathophagidae: Dung flies

Family Cleridae: Checkered beetles

Family Sepsidae: Black Scavenger flies

Family Trogidae: Hide beetles

Family Sphaeroceridae: Small and minute dung flies

Family Scarabaeidae: Scarab beetles

Family Stratiomyidae: Soldier flies

Family Nitidulidae: Sap beetles

Family Phoridae: Humpback and scuttle flies

 

Family Psychodidae: Moth and sand flies and Owl Midges

 

Forensic Entomology Glossary

  • Degree day - a unit measuring how hot or cold it has been during a specific 24 hour period. Every insect species needs a certain number of degree-days to complete their development. One degree-day is equal to the amount of development that occurs in one day when the temperature lies one degreee above the lowest temperature threshold of that insect's ability to grow.
  • ADD or Accumulated Degree Days - .Each day the temperature is above the lowest developmental threshold, the more degee days that accumulate. For example, 5° above the lowest developmental threshold in a 24 hour period is equal to 5 degree days.
  • Entomologist - a scientist who studies insects.
  • Forensic entomology - the study of insects associated with a human corpse in order to determine elapsed time since death or injury to be applied as reliable evidence in criminal or civil cases.
  • Instar - The stages of an insect or arthropod between moults.
  • Larvae - a stage of development in the life cycle of an insect. They are also referred to as maggots (mainly in reference to fly larvae) and do not have legs or noticeable heads.
  • Moult - When the insects or arthropods shed their exoskeleton (outer body covering).
  • Physiological time - this is a measure of how much heat is required to complete an organism's development.
  • PMI - Post-mortem Interval also known as time of death.

Faunal Succession On A Corpse

As a corpse decays, insects arrive in a predictable sequence. This predicatable appearance of various organisms is known as insect succession or faunal successoin.

  • Succession patterns are determined by entomologists for a variety of regions and conditions through the use of controlled experiments.
  • The information from these experiements is used to determine PMI of a corpse in a crime scene.

A number of environmental factors affect the development of individual organisms and the faunal succession:

  • season (average daily temperature)
  • sun exposure
  • location of the body (inside a building or car, in an urban or rural setting
  • body discovered immersed in water or on dry land
  • body found on the ground, or burnt or hanged also will affect faunal succession.

Estimating Time Of Death

Estimating the PMI is the most important function of the forensic entomologist. Two main factors are relevant in determining PMI:

  1. the time taken for each fly species to reach the body;
  2. the rate of development for each species.

Forensic entomologists need to determine the age of the insects on the body since it is known that insects arrive at a body shortly after death and in a particular order. In order to accomplish this feat, the insects on the body must be identified to the species level. Most species are identifed using a classification key.

Typical Sequence Of Insect Arrival On A Cadaver

Succession WaveInsectApproximate Time of ArrivalState of CorpseAge of Corpse

1

Blow flies (Calliphoridae)-spring/summer

From minutes to several hours

Fresh

First three months

 

Winter gnats (Trichocera sp.) - fall/winter

 

 

 

2

Blow flies and Flesh flies

From minutes to several hours. Usually arrive after Blow flies but may arrive first in some circumstances.

Odor

 

3

Dermestid Beetles

 

Fats are rancid

3-6 months

4

Various flies

 

 

 

5

Various flies and beetles

 

Ammonia fermentation

4-8 months

6

Mites/ Piophila casei (Cheese skippers)

 

dry

6-12 months

7

Dermestid Beetles

 

Completely dry

1-3 years

8

Beetles

 

 

3-5 years

Skills Required by Forensic Entomologists outside the Parameter of Traditional Entomology

  • Must be fluent in the procedures of law enforcement and law.
  • Must be able work well with law enforcement personnel.
  • Must be able to work well within the influence of time constraints and media attention.
  • Must be able to deal with unique situations that differ from conventional entomology.

Educational Requirements For A Forensic Entomologist

In order to become a forensic entomologist the following educational requirements are a must:

  • Earned M.S. or Ph.D. in Entomology
  • Graduate coursework which specializes and concentrates on the forensic application of entomology
  • At least five years of case experience applying principles of forensic entomology.
  • Five case exemplars available to submit to the review board (American Board of Forensic Entomology)
  • Pass a written examination with a score of 80% or higher.
  • Pass a practical examination and case work-up on a mock case with a score of 80% or higher.

Educational Programs Providing Training in Forensic Entomology

Careers in Forensic Entomology

Resources Used

Anderson, Gail. Forensic Entomology: The Use of Insects in Death Investigations.

Hall, Martin. Natural History Museum. Maggots and murders: Forensic entomology. 2012.

Benecke, Mark. Forensic Science International. A brief history of forensic entomology. 2001.

University of Western Australia Center for Learning Technology. Forensic Investigations. Forensic Entomology. December 13, 2007.

Comments

Teresa Coppens (author) from Ontario, Canada on November 20, 2012:

Thanks for reading and commenting. Glag you enjoyed it and could relate on a personal level.

Jayme Kinsey from Oklahoma on November 19, 2012:

Very interesting hub! The entomology aspect was always my favorite part about the original CSI show, and lately I have seen it crop up more and more in different books and case studies too. When we ran our ranch, we used a crude sort of entomology everyday to determine things about the livestock. Maybe that is why it is so fascinating to me.

You did an amazing job compiling this information. The formatting and arrangement is beautiful!

Teresa Coppens (author) from Ontario, Canada on October 24, 2012:

Thaks billy. I too am a big mystery fan. I'm also a biology major and if I could have a do over in life this would actually be a career I would consider. Glad you enjoyed the hub!

Bill Holland from Olympia, WA on October 23, 2012:

I read a lot of mysteries and more and more I am seeing this in the plot, so I'm at least a little aware of what this hub is about. Great job of compiling information, Teresa!

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