Forensic Entomology Ch 9 Pgs 135-159. I. Introduction 1. Entomology is the study of insects. 2. Forensic Entomology is the study of the insects associated.

Forensic Entomology

Ch 9

Pgs 135-159

I. Introduction

1. Entomology is the study of insects.

2. Forensic Entomology is the study of the insects associated with a dead body.

3. Insects colonize a dead body almost immediately after death, (assuming the season is correct)

Their rate of development can be used to determine time of death, from a few hours up to a year!

4. After 72 hours, entomological evidence is the most accurate, and sometimes the only, method of determining the time elapsed since death.

5. Insects can be used to determine: Whether the body has been

moved after death Whether the body has been

disturbed The presence or position of

wound sites Whether the victim used

drugs or was poisoned The amount of neglect or

abuse in living victims Solve wildlife crimes

II. Why is it so important to determine the time of death?

6. Determining the time of death is important to the families and loved ones.

Understanding the how, what, when and where give closure.

7. May help to solve crimes, lead to the success of the police investigation, disprove or support an alibi, and determine the victims activities and associations n in the period prior to the crime.

III. History of Forensic Entomology

8. Forensic entomology is one of the oldest sciences used in death investigations.

1st recorded --- 13th century China Modern use --- France 1800’s Took hold in the US in the 1970’s 1996 --- the American Board of Forensic

Entomology was founded

IV. What kind of training do you need?

9. Forensic Entomologists must have extensive training in entomology and insect ecology.

required to be Board Certified. Are usually employed as University

Professors

V. How do you Determine the Time of Death using Forensic Entomology?

10. There are two methods for determining the elapsed time since death:

1. the predictable development of Larval blowflies

2. the predictable, successional colonization of the body by a sequence of carrion insects

11. The method used is determined by the circumstances of each case:

the first method is used when death occurred less than a month prior to discovery.

the second method is used when the corpse has been dead for a month up to a year or more

VI. Using Blowflies – 1st method

12.The method of using maggot age and development can give a date of death accurate to a day or less, or a range of days, and is used in the first few weeks after death. Maggots are larvae or immature stages of Diptera or two-

winged flies. The insects used in this method are those that arrive first on

the corpse, that is, the Calliphoridae or blowflies. These flies are attracted to a corpse very soon after death.

They lay their eggs on the corpse, usually in a wound, if present, or if not, then in any of the natural orifices. Their development follows a set, predictable, cycle.

13. Life Cycle: pg 138-141

1- The insect egg is laid in batches on the corpse

2-hatches into a first instar (or stage) larva. 3- the larva feeds on the corpse 4- molts into a second instar larva. 5- the larva continues to feed and develop

into a third instar larva. **This stage can be determined by size and the

number of spiracles (breathing holes).**

6- the third instar larva continues to feed for a while then it stops feeding and wanders away from the corpse, to find a safe place to pupate.

7- This non-feeding wandering stage is called a prepupa. The larva then loosens itself from its outer skin, but remains inside.

8-This outer shell hardens, or tans, into a hard protective outer shell, which shields the insect as it metamorphoses into an adult.

9-After a number of days, an adult fly will emerge from the pupa and the cycle will begin again. When the adult has emerged, the empty pupal case is left behind as evidence that a fly developed and emerged.

14. An analysis of the oldest stage of insect on the corpse and the temperature of the region in which the body was discovered leads to a day or range of days in which the first insects laid eggs on the corpse. This, in turn, leads to a day, or range of days, during which death occurred.

VII. Using Insect Succession – 2st method

15. This method is based on the fact that a human body goes from the fresh state to dry bones in a matter of weeks or months depending on geographic region.

16. Different stages of the decomposition are attractive to different species of insects. These first groups of insects are the Calliphoridae or

blowflies and the Muscidae or houseflies.

Other species are not interested in the corpse when the body is fresh, but are only attracted to the corpse later such as the Piophilidae or cheese skippers which arrive later, during protein fermentation.

Some insects are not attracted by the body directly, but arrive to feed on the other insects at the scene.

17. Lack of a specific pupae or insect, such as blowfly, could reflect death occurring at a different time of year

18. Conditions affecting colonization also include: Altitude, geographic region, sun exposure Inside or outside a house Buried or above ground Hanged, burned, wrapped or in a vehicle

VIII. Presence and Position of Wounds

19. Blow flies are attracted to wounds Female flies are genetically programmed

to find wounds to lay eggs at that site Irregular Insect colonization may indicate

a wound

IX. Drugs and Entomology

20. Drugs in a body can impact the development of insects that feed on the body Insects can be analyzed for presence of

drugs Blowflies retain toxin throughout larval

and puparial stages

X. Human and Animal Neglect or Abuse

21. Live humans or animals can have dead organic matter on their bodies Material ( sore, wound,

gangrenous material) is attractive to blow flies

Insects actually feed on dead material and clean wounds

Presence of insect can assist in determining how long wound has been present

XI. Collection of Entomological Evidence

22. Entomological evidence should be collected at crime scene Remains and environment should be

observed and photographed before collection of insect stages begins

Thermometer placed on top of maggot masses to measure temperature

23. Blowfly evidence should be collected at all stages of development: Eggs – collect clump size of a dime

Preserve 1/2 of sample in alcohol mixture Other half kept alive and placed in vial with beef liver Eggs must be regular observed to determine actual time of

hatch Number of eggs hatched and when first hatch occurred should

be recorded

After taking temperature of any masses of maggots, a sample should be collected and stored separately from each major mass, including large and small maggots from each mass Place in alcohol mixture or hot water Place samples of live maggots in vial, however, do not

overcrowd, and include food source- beef liver Check area for prepupal third instar larvae

Pupae – collect and place in vial with paper towel to cushion them- do not preserve Pupae are generally found buried in dirt several

centimeters deep scattered several meters away from body

Empty pupal cases should be collected Adult blowflies have little forensic value, unless they are

still wet and emerging from pupae Collect and label as undeveloped fly

24. Other insect collection: While blowflies are predominant insects

used to determine death in the first few weeks after death, other insects such as flies and beetles should be collected and preserved in alcohol

Beetles must be stored individually, as they will eat other smaller beetles and flies