entomology is the study of insects. reconstructing the circumstances of death forensic taphonomy ...

Entomology is the Study of Insects

Reconstructing the circumstances of death

Forensic Taphonomy

Estimating the time of death

What is Forensic Entomology?The use of insects and their arthropo

d relatives that inhabit decomposing remains to aid legal investigations.

Insects and other arthropods can be used to answer:

Forensic Entomology

How or where a death occurred.

Postmortem Interval (PMI): Time between death and discovery of a corpse.

When did death occur?

Three Areas of F. Ent. Medicolegal - focuses on the criminal component of t

he legal system and deals with the necrophagous (or carrion) feeding insects that typically infest human remains

Urban Pests- deals with the insects that affect man and his immediate environment. The damage caused by their mandibles (or mouthparts) as they feed can produce markings and wounds on the skin that may be misinterpreted as prior abuse.

Stored product pests- commonly found in food and the forensic entomologist may serve as an expert witness during both criminal and civil proceedings involving food contamination.

The History of FE In 1235 A.D., Sung Tz'u, a Chinese "death investig

ator," demonstrated knowledge of blow fly activity on bodies relative to those orifices infested, the time of such infestation, and the effect of trauma on attractiveness of tissue to such insects.

Francesco L. Redi (1668) Bergeret (1855), near Paris, France, was the first w

esterner to use insects as forensic indicators. Between 1883 and 1898, J. P. Megnin in France pu

blished a series of articles dealing with medicocriminal entomology.

Why Call a Forensic Entomologist?

Most commonly called upon to determine the postmortem interval or "time since death" in homicide investigations. Use a number of different te

chniques including species succession, larval weight, larval length, and a more technical method known as the accumulated degree hour technique which can be very precise if the necessary data is available.

Make inferences as to possible

postmortem movement of a corpse.

Freezing or wrapping of the body may be indicated by an altered species succession of insects on the body.

Determine the circumstances of abuse and rape.

The insects recovered from decomposing human remains can be used for toxicological analysis

Forensic Entomology

What is an arthropod?

What is an insect?

Review Definition of Forensic Entomology:

Study of insects and their arthropod counterparts that interact with legal matters.

InsectsInsects are a class of Arthropods that have three segments to their body, one pair of antennae, three pairs of legs, compound eyes and breathe air via small holes or spiracles along the side of their body.

InsectsMost arthropods are insects BUT there are also bugs that are NOT insects such as spiders (Arachnida), crayfish & woodlice (Crustacea) and millipedes & centipedes (Diplopoda & Chilopoda - sometimes collectively known as Myriapoda).

It is easy to be confused!

InsectsClassification of the arthropods can also be slightly different in various information sources.

To make it even more confusing, as more research is done, scientists may revise or even change what group various organisms belong in.

InsectsAs you watch the slide presentation, think about the following:

• Are there ‘good or bad’ insects?

• What role do insects play in science?

• Are insects important in forensic science?

Forensic Entomology

Arthropoda (phylum)

class - Arachnida (spiders, scorpions)

class - Chilopoda (centipedes)

class – Insecta (insects)

order – Hymenoptera (ants, bees, wasps)

order – Blattaria (cockroaches)

order – Diptera (flies)

order – Coloeoptera (beetles)

Important Insects 1. Blowflies

Blow fly eggs can provide investigators with an accurate estimate of postmortem interval (PMI) and allow investigators to narrow their focus

Maggots Growth takes several days to several weeks depending upon species, environmental conditions, and the number of larvae present.

Adult Blow-Fly Differ in abundance from region to region, from habitat to habitat, and from season to season.

Forensic Entomology

Flies

Some flies are attracted to dead bodies.

Calliphoridae (blow flies) Sarcophagidae (flesh flies) Muscidae (house flies) Phoridae

Carrion Flies:

Forensic Entomology

Phoridae

Scuttle flies or coffin flies

Take advantage of physical barriers; larger flies can’t get to body

Forensic Entomology > Flies

Calliphoridae (blow flies)

Shiny color (bluebottle, greenbottle)

Among the first to arrive at a corpse

Green blow fly

Phaenicia sericata Joseph Berger, www.insectimages.org

Forensic Entomology > Flies

Sarcophagidae (flesh flies)

Large, gray flies

Also among the first flies to arrive

Flesh fly

Courtesy Ian Dadour, UWASarcophagidae - Family

Forensic Entomology > Beetles

Forensic Entomology > Beetles

Coleoptera (beetles)

Arrive early or late in decomposition process, depending on species

Carrion beetle

Oiceoptoma noveboracensis David Cappaert, www.insectimages.org

Hide beetle

Trogidae Courtesy Ian Dadour, UWA

Forensic Entomology > Flies and Beetles

Complete Metamorphosis

1. Eggs

2. Larvae

3. Pupae

4. Adult

Smooth & Hairy maggots

Courtesy Ian Dadour, UWA

Image: http://www.nlm.nih.gov/visibleproofs

Estimating the PMI

Once insects are collected (both adults and immature), they are used to estimate the postmortem interval (PMI).

Collection of Insect Samples

Estimating the PMI

Can be collected at the crime scene Can be collected during autopsy

For each maggot mass:

Estimating the PMI > Collection

Collect Climatological Data: Environment affects growth rate Collect temperature, humidity, etc.

Kill ½ of the maggots collected: Stops growth for age estimation Preserve in ethanol or Kahle’s solution Preservation prevents bacterial

degradation

For each maggot mass:

Estimating the PMI > Collection

Keep ½ of the maggots alive: The species of maggots can not be

identified (maggots look the same) If maggots are raised to adults, the flies

can be identified to the species level.

?Chrysomyamegacephala

Analysis of Insects

Once evidence is received, the first step is to identify the species of samples.

Estimating the PMI

Identification of Insects

Estimating the PMI > Species Identification

Answer:

Different species grow at different rates

Question:

Why is species identification important?

7-mm maggot may be anywhere from 3 days old to 10 days old, depending on species


Sarcophagid bullata

Timeline:

Egg Larvae Pupa Adult

Sarcophagid cooleyi

50 hours

40 hours 90 hours

110 hours

Identification of the specimen


Morphology Color, hairs and bristles, wing structure Male genitalia

DNA identification Mitochondrial sequence of the gene region

cytochrome oxidase I

After evidence is collected and identified, there are two methods for estimating the PMI:

Estimating the PMI > Analysis

Succession of insect fauna

Estimating the age of immature insects

Facts:

Estimating the PMI > Analysis > Succession

The corpse provides an attractive environment for insects to feed, mate, and deposit eggs.

The corpse passes through relatively predictable stages of decomposition.

Different species of insects will be attracted to the corpse at different times.

Most flies arrive early in the decomposition process.


Calliphoridae(blow flies)

Sarcophagidae(flesh flies)

Beetles can arrive early or late in the decomposition process (species dependant).


Coleoptera (beetles)

Conditions affecting succession:


Temperature (hotter = faster) Geographic region (variable insect fauna) Other factors: wrapped body, buried,

indoors, etc.

Since eggs are rarely deposited on a corpse before death…

Estimating the PMI > Analysis > Age of Immature Insects

The age of immature insect specimens is the absolute minimum amount of time a person has been dead.

For example:

A three-day-old maggot on a corpse would indicate the body has been dead for at least three days.

Remember, flies and beetles undergo complete metamorphosis

Immature specimens = egg, maggot, pupa


1. Eggs

2. Larvae

3. Pupae

4. Adult


The first step in age identification is to identify what stage the insect is in.

2. Larvae


Larvae grow in three stages called instars. During the 3rd instar, maggots will stop

feeding, leave corpse, and pupate.

If the samples are maggots, the molting stage can be identified.

Instar can be determined by looking at spiracles.



3 “footballs” = 3rd instar 2 “footballs” = 2nd instar Glob = 1st instar

Phaenicia sp

Spiracles are complete

Third-instar larvae

Phormia regina

Spiracles are incomplete

Third-instar larvae

Five Stages of Decomposition Fueled by Insect Activity.

FreshBloatDecayPost-decayDry (skeletal)

CRIME SCENE CREATURES

Fresh

Begins at death Flies begin to arrive Temperature falls to

that of the ambient temperature.

Autolysis, the degradation of complex protein and carbohydrate molecules, occurs.

Results: Fresh Stage

Flies began to arrive within minutes of pig placement however, laying of eggs was delayed 12-18 hours.

There was already some green discoloration on Pig 2 at the beginning of the fresh stage, possibly due to the fact that it was dead about 8 hrs before Pig 1.

72 hrs later, the first signs of bloating occurred, ending the Fresh Stage.

Bloat

Swells due to gases produced by bacteria

Temperature rise of the corpse

Flies still present

Results: Bloat stage

At about 72 hours, noticeable bloating began to occur in Pig 1.

However, Pig 2 did not show visible signs of bloating until about 92 hours.

The gap between the two pigs might have been even greater if they had both died at exactly the same time.

Decay Gases subside,

decomposition fluids seep from body.

Bacteria and maggots break through the skin.

Large maggot masses and extreme amounts of fluid.

Unpleasant odor Larvae beginning to

pupate. Corpse reduced to

about 20% of it’s original mass.

Results: Decay Stage

Decay stage started around 102 hours. At this point, the maggots had broken the skin and

the pigs had begun to deflate. Decompositional fluids began to seep from the

carcass. There was a green froth around the pig and also a

dark fluid ring around the body of Pig 1. Maggot activity increased tremendously, and maggot

mass temperature reached its high during this stage.

Post-Decay Carcass reduced to

hair, skin, and bones.

Fly population reduced and replaced by other arthropods.

Hide beetles are dominant in dry environments.

Mite and predatory beetle populations increase.

Results: Post-decay Stage

When the experiment was terminated due to the fact that maggot activity had ceased, the pigs had reached the Post-Decay Stage.

They were mostly skin, bones, and hair, but there was some tissue remaining.

Dry (Skeletal)

Does not always occur especially if corpse is in a wet region. Maggots will stay longer and hide beetles will not appear.

In wet environments the hide beetles are replaced with nabid and reduviid insects.

The corpse is reduced to at least ten percent of the original mass.

In the last stage (Skeletal Stage), only bone and hair remain.

Succession of Insects on the Corpse Estimates of postmortem intervals based on insects

present on the remains are based on:• The time required for a given species to reach a particular stage

of development.• Comparisons of all insect species present on the remains at the

time of examination. Ecological succession occurs as an unexploited habitat

(like a corpse) is invaded by a series of different organisms.

The first invasion is by insect species which will alter the habitat in some form by their activities. These changes make the habitat attractive to a second wave of organisms which, in turn, alter the habitat for use by yet another organisms.

Beetles- generally found on the corpse when it is more decomposed. Rove Beetles - Family Staphylinidae Hister Beetles - Family Histeridae Carrion Beetles - Family Silphidae Ham Beetles - Family Cleridae Carcass Beetles - Family Trogidae Skin/Hide Beetles - Family Dermestidae Scarab Beetless - Family Scarabaeidae Sap beetles - Family Nitidulidae

Ecology of Decomposition

Necrophages - the first species feeding on corpse tissue. Includes rue flies (Diptera) and beetles (Coleoptera).

Omnivores - species such as ants, wasps, and some beetles that feed on both the corpse and associated maggots. Large populations of ominvores may slow the rate of corpse’s decomposition by reducing populations of necrophagous species.

Parasites and Predators - beetles, true flies and wasps that parasitize immature flies.

Incidentals – pill bugs, spiders, mites, centipedes that use the corpse as an extension of their normal habitat

Insect species arrive at a corpse in waves like clockwork Calculate the heat/thermal energy

(accumulated degree hour) required for each stage of the Green Bottle Fly’s life cycle.

Possibly the greatest potential source of error in using arthropod successional patterns lies in the collection of speciments.

Must only be done correctly to accurately sample the insects.

Two Different Maggot Generations

These are

distinguishable by the length and obvious size difference.

This is why we believe there are two peaks in our graph data for the Sunlit Pig.

The photograph was taken at a time consistent with the influx at 132 hours.

Maggot Mass


PMI estimation can be made based on the stage of the immature specimen.

Species and temperature must be known.


PMI estimation can be made based on maggots size or development in pupa.

Species and temperature must be known.


Temperature (hotter = faster) Other factors: drug use, day length

Conditions affecting growth rate:

Sample Investigation

Dead body discovered at the crime scene (9:00am)

Maggots are found on the body

Details of the Case:

Some maggots are collected and preserved; some are collected alive

No irregular circumstances; temp recorded Main suspect claims to have seen the

victim alive 2 nights earlier.


Evidence:

Additional maggots kept alive for identification

16 maggots preserved


Identifying the Sample:

= Cochliomya macellaria


Measuring the maggots:

Largest size = 15 mm

Average = 14.3 mm

14 15 14 14 15 14 15 13 13 15 15 14 15 13 15 14 (mm)


Maggots are about 96 hours old.

Age of maggot (hours)

Maggot Crop Analysis

Maggot as a Source of Human DNA

Maggots store food in their crops as they feed. During later stages of larval development, the

contents of the crop is emptied into the gut

CROP

Mouth Posterior

For example:

In Calliphora vicina at room temperature, the crop is full after 3 days and is emptied by 7 days (approximate)

DNA is found in the cells in our body.

Nucleus(Brain of the cell)

Mitochondria(more later)

Forensic DNA Review

Identification of maggot crop contents would be helpful in three situations:

1. Corpse is removed from suspected crime scene


A murder victim remains undiscovered.

Flies discover the corpse and lay eggs.

Maggot Crop Analysis > Corpse Removed

Maggots hatch and feed on the corpse.


Murder victim is removed from crime scene.

The maggots remain.


Crop will contain Human tissue



2. There is a question as to the origin of a maggot used in a PMI estimation


A turkey is thrown into a dumpster.

Maggot Crop Analysis > Maggots from Other Source

Three days later, maggots have developed on the turkey.


Also three days later, a dead body is thrown into the dumpster.


The maggots migrate from the turkey to the human body.


Crop will contain Turkey tissue or a mixture of Turkey/Human tissue



3. There may be a chain of evidence dispute.


Here you go!

Thank you!

Maggot Crop Analysis > Chain of Evidence Dispute

They’re 5 days old!

These aren’t the maggots I gave you.

2 days later...

Are too!Are not!

Maggot Crop Analysis > Chain of Evidence Dispute


Poor quality of samples usually prevents analysis.

Maggot Dissection

Maggot before dissection

Cut off posterior segments

Maggot Dissection

Ventral incision of the cuticle

Maggot Dissection

Peel back cuticle to reveal crop

Maggot Dissection

Remove crop

Maggot Dissection

Case Study 1: http://www.research.missouri.edu/entomology/casestudies.html On a midmorning in August, the half-nude body of a young female was

discovered, more or less face down, among a group of junk automobiles near Spokane, Washington. The victim had died of multiple stab wounds to the chest and neck, and adult blow flies were observed in and around the wounds. Blow fly eggs were collected from the wounds at autopsy in the late afternoon. Subsequent dissection of the eggs showed no embryonic development suggesting that they had been deposited on the remains less than eight hours earlier.

The victim had been last seen alive during the evening two days prior to her discovery. The insect evidence, however, suggested that the young woman had been murdered during the hours of darkness preceding the finding of her remains. Had the victim died any earlier, young fly larvae (maggots) rather than eggs would have been collected from her wounds. Climatic conditions on both days prior to her discovery were suitable for adult blow fly activity and egg laying. A subsequent investigation verified these findings, revealing that the victim had been murdered during the hours of darkness just prior to the morning of her discovery.

Case Study 2 On 4 June the partially clad body of a young

female was found alongside a rural highway in the northwestern United States. An autopsy revealed that she had died of multiple head and neck wounds inflicted by a heavy sharp object. She was subsequently identified as a 14-year old prostitute. Her brother reported her as missing approximately four days prior to discovery of her corpse. 1

She had last been seen alive on the morning of 31 May in the company of a 30-year old army sergeant, the primary suspect. While considerable circumstantial evidence supported the theory that the victim had been murdered by the sergeant, an accurate estimation of time of death was crucial to establishing a possible link between the suspect and the victim at the time when death occurred.

Numerous fly larvae (maggots), adult flies, and other insects were observed and collected in and around the victim's wounds. Some were placed alive in small containers and subsequently reared to produce adult flies. Others were placed immediately into a liquid preservative. Additional specimens collected at the autopsy were processed in a similar manner. Numerous photographs of the crime scene, the surrounding vegetation and terrain, and the corpse were taken. These photographs included enlargements illustrating the adult flies and maggots present at the time the body was discovered.

Based on this total array of evidence, entomologists determined that the first insects to colonize the remains had arrived on 31 may. The insect evidence indicated a PMI of four days.

Based on this evidence, the army sergeant with whom the victim had been last seen alive was arrested and charged with first degree murder. On questioning he admitted to having murdered the victim by striking her six to eight times with a small hatchet sometime around noon on May 31. Subsequently, he entered a plea of guilty to the murder charge and was sentenced to life in prison without parole.

Case Study 3 The remains of a murder victim were reportedly thrown

down an open well on a small farm in a rural area in south-central Indiana. Then the well was completely filled with junk, tires, and rocks. The exact location of the well where the remains were deposited was unknown, but as the investigators drove into one of several wooded farm yard sites being investigated, it was obvious they had found the right location. Several thousand flies were hovering over a pile of old tires. The remains were found at the bottom of the well under the debris. Decomposition was advancing in the body, but there were no insects found on it. Access to the body by the blow flies was prevented by the intervening material, but odors were still capable of attracting multitudes of insects.

Famous Trial with an Entomological Twist

“The pile of evidence painstakingly assembled by prosecutors in Westerfield‘s capital murder case got a jolt last week from an entomologist who suggested that insect evidence from the 7-year-old’s body may exonerate the defendant, who is accused of abducting Danielle from her bedroom, killing her and then dumping her body.”

Searchers found the second-grader in a trash-strewn lot three and a half weeks after she vanished. Her body was badly decomposed and the medical examiner could only offer prosecutors a wide range — 10 days to six weeks — for her time of death.

Investigators hoped Faulkner could narrow that window to Feb. 2, 3 or 4, the days immediately following Danielle's abduction when Westerfield's activities seemed suspect. Faulkner examined maggots from her body and told authorities the insects began growing 10 to 12 days prior, putting the first infestation between Feb. 16 and Feb. 18. Infestation can start as soon as 20 minutes after a dead body is dumped outdoors.

Faulkner's conclusion did not fit prosecutors' theory. Westerfield was under constant police surveillance from Feb. 5 until his arrest, offering him no opportunity to dump her body in the window of time the entomologist's testimony indicated. Faulkner quickly became a witness for the defense.

Westerfield was convicted and senteced to death for the murder of the young girl.

On a mid-November afternoon, police were called to investigate a foul-smelling odor emanating from a single-family home in the southeastern United States. It did not take long for the investigating officers to discover a shallow grave in the dirt basement of the house, which contained the badly decomposed body of a young female.

It was immediately apparent that the victim had died of a single bullet wound to the head inflicted by a small caliber rifle. A scrupulous examination of the corpse and excavation of the soil in and around the grave site by a forensic entomologist working with police revealed the presence of numerous larvae and pupae of two different fly species.

The specimens were collected from the scene and brought back to the laboratory to be reared. Supplemental information, including weather data and soil temperature, was also analyzed in order to determine the principal climatic conditions at the death site. Based on the developmental biology of both species of flies in that environment, the forensic entomologist estimated that the specimens associated with the body the longest were in their fourth stage of development. It was estimated that the victim had died approximately 28 days prior to the date her body was discovered.

This specific information allowed the authorities to target their investigation in and around the estimated time of death. Within a short time, they identified a female suspect who eventually confessed to having killed the victim precisely 28 days prior to the time the body was found. She further admitted to attempting to bury the victim in a shallow grave in the basement of the house after committing the homicide.

Calculating the developmental rate of the flies provided investigators with the only scientifically reliable method of estimating the time of the victim’s death and subsequently led to the arrest and conviction of the killer.

entomology is the study of insects. reconstructing the circumstances of death forensic taphonomy ...

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use of insects

study of insects

insects classification

time of death slide

carrion feeding insects

forensic entomologist

toxicological analysis