Warm-Up September 15, 2014

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Warm-UpSeptember 15, 2014

• How is forensic entomology used to solve crimes?


Objective

• SWBAT estimate the time of death using entomology.


Agenda

1. Crime 360

2. Life Cycle of Fly

3. PMI/Time of Death

4. Real CSI Video

5. Crime Solving Insects

6. Exit Slip

T. Trimpe 2008 http://sciencespot.net/

Crime 360Forensic Entomology

1. What does a forensic entomologist study?A. Worms B. Insects C. 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 deathB. Helps investigators determine how a person was killedC. Helps investigators determine what the person ate at his/her last meal

4. What stage of a fly’s life cycle are maggots?A. Adult B. Pupa C. Larva

5. In what kingdom are maggots classified?A. Plants B. Animals C. Fungi

Watch the video and then answer the questions.

http://www.aetv.com/crime-360/video/forensic-tools-forensic-entomology

1. What does a forensic entomologist study?A. Worms B. Insects C. 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 deathB. Helps investigators determine how a person was killedC. Helps investigators determine what the person ate at his/her last meal

4. What stage of a fly’s life cycle are maggots?A. Adult B. Pupa C. Larva

5. In what kingdom are maggots classified?A. Plants B. Animals C. Fungi

The answers are …

speciesage


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.


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.


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


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

1st instar


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

1st instar


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

1st instar

2nd instar


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

1st instar

2nd instar

3rd instar (feed)


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

1st instar

2nd instar

3rd instar (feed)


Fly life cycleThe 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

1st instar

2nd instar

3rd instar


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

1st instar

2nd instar

3rd instar

Pupae

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!

http://www.jeffersonbass.com/video_body_farm_tour.html


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.



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.


Body Temperature

Rigor MortisPost-Mortem

Interval

Warm Far extremities and small muscles only < 3 hours

WarmMiddle extremities

and medium muscles

3 – 8 hours

Cold Throughout body 8 – 36 hours

Cold None > 36 hours



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.



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.



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.


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


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.


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 1st instar at 70˚F, then 1610 degree-hours would have accumulated.


Calculating PMI fromAccumulated Degree Hours (ADH)

From To Temp Hours ADH Total

Egg 1st Instar 70° F 23 1610 1610

1st Instar 2nd Instar 70° F 27 1890 3500

2nd Instar 3rd Instar 70° F 22 1540 5040

3rd Instar Pupa 70° F 130 9100 14140

Pupa Adult Fly 70° F 143 10010 24150


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


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.


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.


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?

T. Trimpe 2009 http://sciencespot.net/

Presentation developed for use with the Crime Solving Insects activity available at http://ipm.ncsu.edu/4-H/CSIfinal.pdf.

Image: http://www.animals-in-distress.net/files/photos/coriander2.jpg

What happened to Porky?

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.

• 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.

http://www.cmnh.org/site/Img/ResearchandCollections/InvertZoo/124_blowflylifecycleRW.jpg

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.

Stages of Decay1 - 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.

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.

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

Case #2: Canine CaperPolice 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.


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

Case #3: Dandy’s DeathPolice 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.


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

Case #4: Porky’s PerilPolice 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.


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


Homework

• Unit 2 Review due Tuesday

• UNIT 2 EXAM ON WEDNESDAY


Exit SlipSeptember 15, 2014

1. 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 417101 for the room number.

QUESTION: How can you use entomology to determine the time of a person’s death?

Documents

Warm-Up September 15, 2014