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Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. www.CrosscuttingConcepts.com Warm-Up September 15, 2014 How is forensic entomology used.

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Presentation on theme: "Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. www.CrosscuttingConcepts.com Warm-Up September 15, 2014 How is forensic entomology used."— Presentation transcript:

1 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Warm-Up September 15, 2014 How is forensic entomology used to solve crimes?

2 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Objective SWBAT estimate the time of death using entomology.

3 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Agenda 1.Crime Life Cycle of Fly 3.PMI/Time of Death 4.Real CSI Video 5.Crime Solving Insects 6.Exit Slip

4 T. Trimpe Crime 360 Forensic Entomology

5 1. What does a forensic entomologist study? A. WormsB. InsectsC. Spiders 2. Fill in the missing information in this statement: An entomologist needs to know the type of fly ____________ and the _________ of the larva in order to help the investigators. 3. How can a blowfly help an investigation? A. Helps investigators determine the time of death B. Helps investigators determine how a person was killed C. Helps investigators determine what the person ate at his/her last meal 4. What stage of a fly’s life cycle are maggots? A. AdultB. PupaC. Larva 5. In what kingdom are maggots classified? A. PlantsB. AnimalsC. Fungi Watch the video and then answer the questions.

6 1. What does a forensic entomologist study? A. WormsB. InsectsC. Spiders 2. Fill in the missing information in this statement: An entomologist needs to know the type of fly ____________ and the _________ of the larva in order to help the investigators. 3. How can a blowfly help an investigation? A. Helps investigators determine the time of death B. Helps investigators determine how a person was killed C. Helps investigators determine what the person ate at his/her last meal 4. What stage of a fly’s life cycle are maggots? A. AdultB. PupaC. Larva 5. In what kingdom are maggots classified? A. PlantsB. AnimalsC. Fungi The answers are … species age

7 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Carrion Flies Many organisms use “carrion”, or carcasses, as a food source. Some fly species specialize in living on carrion. These carrion flies are the most important insects to the forensic entomologist.

8 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Carrion Fly Families There are two families of carrion flies: the blowflies, in the family Calliphoridae, and the flesh flies, in the family Sarcophagidae. Adult calliphorid flies are easily identified by their iridescent blue, green, copper, or black bodies. Sarcophagid flies, on the other hand, are grayish, usually with three distinct longitudinal dark stripes on the dorsal thorax.

9 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Fly life cycle The adult female fly lays her eggs on the exposed tissue within minutes of death. She lays all eggs in one sitting, but may return to the same site to lay again several times over the course of her 2-3 week lifespan. egg adult

10 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Fly life cycle The eggs hatch within approximately 24 hours of being laid. Fly larvae, known as maggots, are now in the first instar stage. They crawl to the closest food source and begin to eat. egg adult 1 st instar

11 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Fly life cycle The first instar maggots are small and do little more than eat to support their rapid growth. Over the next 27 hours, they will double in size until their skin literally can’t hold them anymore. egg adult 1 st instar

12 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Fly life cycle The maggots shed their old skin and are now considered second instar maggots. This stage is very similar to the first instar in that the maggots continue to devour their food source and grow rapidly. egg adult 1 st instar 2 nd instar

13 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Fly life cycle After another 22 hours, these maggots will have reached the maximum size their current skin will allow and they will shed once more. They are now in their third instar egg adult 1 st instar 2 nd instar 3 rd instar (feed)

14 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Fly life cycle The third instar stage is divided into two halves, the feeding third instar and the migrating third instar During the first half, the maggots continue to eat, storing up as much energy as possible. egg adult 1 st instar 2 nd instar 3 rd instar (feed)

15 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Fly life cycle The second half of the third instar begins when the maggots stop eating and begin to move away from their food source. The maggots will move to a patch of soil where they can burrow and begin the next life stage. Overall, the maggots spend about 100 hours in their third instar. egg adult 1 st instar 2 nd instar 3 rd instar

16 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Fly life cycle Once burrowed, the maggots enclose themselves in a hard shell and begin the metamorphosis (change) that will result in an adult fly. At this stage, the maggots are now known as pupae. egg adult 1 st instar 2 nd instar 3 rd instar Pupae

17 Did you know… The “Body Farm” in Knoxville, Tennessee is a university research facility to investigate human decomposition under various conditions in order to understand the factors which affect its rate. Click the image to view a video about the Body Farm!

18 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. The Post Mortem Interval Forensic entomology provides data used to estimate the time that elapsed between the actual death and when the body was first discovered. This period is referred to as the post mortem interval, or PMI.

19 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. The Post Mortem Interval Recent PMI (0-50 hours) is estimated by a medical examiner or forensic pathologist based on physical changes to the cadaver. If a body remains exposed to the environment for a longer period of time, the normal physical changes observed after death may not provide an accurate PMI estimate.

20 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Body Temperature Rigor Mortis Post-Mortem Interval Warm Far extremities and small muscles only < 3 hours Warm Middle extremities and medium muscles 3 – 8 hours ColdThroughout body 8 – 36 hours ColdNone > 36 hours

21 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. The Post Mortem Interval Cadavers decompose in four stages: fresh, bloated, decay, and dry. The time the body spends in any individual stage will vary depending on environmental conditions; warm, wet weather speeds decay, while cold, dry weather slows it.

22 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. The Post Mortem Interval Different insects are attracted to each of the four different stages of decomposition. The ordered series of insects attracted to the decomposing body is called a succession. The succession pattern is useful in estimating how long a cadaver has been exposed to the insects.

23 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. The Post Mortem Interval For example, carrion flies are attracted to a bloated corpse, therefore they will only be present on a corpse once that stage is reached. Adult blowflies, however, are attracted to the fresh corpse and lay their eggs rapidly after death.

24 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Factors influencing decay Most important environment factors in corpse decay: Temperature Access by insects Depth of burial Other Factors Chemical-- embalming agent, insecticides, lime, etc. Animals disrupting the corpse

25 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Factors influencing decay Entomologists develop and maintain succession databases. When a crime scene is investigated, the forensic entomologist compares the insect species and their distribution of larval stages to the database to estimate the time of death.

26 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Degree-hours The time it takes each life cycle to develop is measured in degree-hours because the development rate is VERY temperature dependent. If an egg takes 23 hours to develop into the 1 st instar at 70˚F, then 1610 degree-hours would have accumulated.

27 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Calculating PMI from Accumulated Degree Hours (ADH) FromToTempHoursADHTotal Egg1 st Instar 70 ° F st Instar2 nd Instar 70 ° F nd Instar3 rd Instar 70 ° F rd InstarPupa 70 ° F PupaAdult Fly 70 ° F

28 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Time of Death vs PMI Time of death and Post-Mortem Interval are usually different because of the assumptions of the PMI calculation. PMI is restricted to the time that the corpse or body has been exposed to an environment which would allow insect activity to begin. This could be affected by factors such as: –Closed windows –Body in box or bag –Cold temperatures –Deeper burial

29 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Important Considerations In addition to the succession of insects on the decaying cadaver, there is a succession of species of insects throughout the year, especially in a temperate climate. Some fly species are active in the early spring, different species are active in the fall, and others are continuously active.

30 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Important Considerations In regions with cold winters, bodies are often discovered when the snow melts in the spring, and investigators are called upon to determine in which season the death occurred. If an insect larvae which is more abundant in the fall is discovered, this can indicate the body was undiscovered for many months, while if larvae are found from spring flies, this could indicate the cadaver is more recent, or that it was recently exposed to the newly emerged adult flies.

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32 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Real CSI Video 10. What is the most common type of gun? 11. If someone is shot and there are no casings at the scene, then what type of gun did they probably use? 12. What is range of fire? 13. What comes out of a fired handgun? 14. Why do ballistics labs test fire the weapon into the water chamber?

33 T. Trimpe Presentation developed for use with the Crime Solving Insects activity available at Image: What happened to Porky?

34 Things to Remember … The progression of insect life follows a pattern, and the developmental rates of flies are relatively predictable. The rate of insect development is influenced by temperature because insects are ectothermic (“cold blooded”), which means their body temperatures are largely dictated by the outside temperature. Only when the outside temperature warms an insect’s internal body temperature to its critical level can the insect become active (and eat and grow). The postmortem interval—the time between death and discovery of the corpse – can be estimated using insect evidence and temperature data along with other factors, such as the presence of drugs in a corpse and conditions related to the corpse itself (wrapped in a material, in a closed room, exposed to outside conditions, etc.) Not all fly species are found everywhere, and this can provide important information also. For example, the skipper fly, Piophila nigriceps (pie-oh-FEEL-ah NYE-greh-cehps), is found only in urban settings. House flies, blow flies, and flesh flies can be found in both urban and rural settings.

35 Flies, beetles, and many other insects have complete metamorphosis, which consists of four stages – egg, larva, pupa, and adult. After the adults mate, the females lay eggs onto corpses - usually near natural body openings or wounds. Metamorphosis Feeding activity is usually seen in the head region first (mouth, nostrils, eyes, ears), followed by the excretory and reproductive openings. The trunk of the body is invaded much later in the process. The length of the life cycle varies between different fly species and is dependent on temperature.

36 Stages of Decay 1 - Fresh Stage Begins at the moment of death and lasts until the body becomes bloated. Blow flies and flesh flies are among the first to find the body. Predatory wasps and beetles may arrive later to feed on the maggots (but not the corpse). 2 - Bloated Stage Begins when the body becomes inflated due to the production of gases from bacteria that begin to putrefy the body or cause it to decompose. House flies now join the other flies and their maggots form feeding masses that help to liquefy the tissues of the body. 3 - Decay Stage Begins when the skin breaks and the gases escape. Maggot masses are large and very active as they grow older and larger. This is the stage of decomposition that smells bad. At the end of this stage, the maggots leave the corpse in search of a place to pupate in the soil. 4 – Post-Decay Stage Most of the flesh is gone from the corpse, with only cartilage, bone, and skin remaining. This stage is devoid of flies. Some beetles continue to feed on the highly desiccated or dried remains.

37 Case Studies For each case: 1 – Review the police report and weather report. 2 – Examine & document the collected evidence. Measure the length of the maggots & pupae. Record your data in a chart. Consult the Species Key and the tables on your lab page to determine the various fly species that were found on the corpse and their ages. 3 – Use the information from the reports and your examination to answer the questions.

38 Case #1: Oh, Deer! Police Report: The body of a female deer was found behind a fence along a busy two-lane road on the edge of the city limits of Charlotte. Animal Control was called and reported no apparent wounds on the body. It was not hunting season. Weather Report: Daytime temperatures have been fairly consistent for the past three weeks, ranging from 70 to 74º F. Questions: 1. Approximately how long has this animal been dead? 2. Why are maggots of different ages found in the body? 3. Other than temperature, what abiotic (external to the corpse) conditions would you want to obtain from the weather station to help you to be more confident of your time of death estimation? Species & Stage Size (mm) Age

39 Case #2: Canine Caper Police Report: The body of a large pit bull terrier was found inside a walk-in basement at a home in Cary. Maggots were found concentrated in the head and region behind the shoulder. The windows were closed, although the open curtains allowed sunlight to enter, and the air conditioner was set at 72º F. Weather Report: Daytime temperatures have been variable over the past three weeks, ranging from 75 to 94º F. Skies have been sunny. Questions: 1. Approximately how long has this animal been dead? 2. What effect, if any, do the outside temperatures have on your estimation of time of death in this case? 3. How does the fact that the windows were closed relate to the populations of flies you observed in and around the corpse? 4. Do you suspect foul play? Explain. Species & Stage Size (mm) Age

40 Case #3: Dandy’s Death Police Report: The body of a young male horse was found in a pasture in a small town near Wilmington. The autopsy from the vet school reveals that the cardiac glycoside, oleandrin (a powerful heart stimulant), was present in the body. Oleandrin is found in the oleander plant. Oleander is a common ornamental shrub in this area, but none grows within 200 feet of the pasture. Weather Report: Daytime temperatures have been unusually warm over the past three weeks, ranging from 84 to 86º F. Questions: 1. Approximately how long has this animal been dead? 2. What effect, if any, does oleandrin have on your estimation of time of death? 3. What effect, if any, does temperature have on your estimation of time of death in this case? 4. Do you suspect foul play? Explain. Species & Stage Size (mm) Age

41 Case #4: Porky’s Peril Police Report: The body of a large pot-bellied pig was found in a dense stand of evergreen trees far from any urban area in Buncombe County. Hairs around the pig’s neck were worn away in a band pattern. Weather Report: Daytime temperatures have been average over the past three weeks, ranging from 70 to 73º F. Temperatures in the woods would be approximately 5 degrees cooler due to the lack of sun in the shady environment. Questions: 1. Approximately how long has this animal been dead? 2. What effect, if any, does temperature have on your estimation of time of death in this case? 3. Do you suspect foul play? Explain. Species & Stage Size (mm) Age

42 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Homework Unit 2 Review due Tuesday UNIT 2 EXAM ON WEDNESDAY

43 Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved. Exit Slip September 15, Get out a mobile device or use one of the computers and go to m.socrative.com. You can also use one of the iPads that has the Socrative app. 2. When prompted, enter for the room number. QUESTION: How can you use entomology to determine the time of a person’s death?


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