Presentation on theme: "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."— Presentation transcript:
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 – 1 st 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 – 2 st 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