Forensic Entomology

The Role of Insects in Medico legal Death Investigation

Forensic Entomology

Forensic Entomology

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Forensic Entomology

is the use of insect knowledge in the investigation of crimes.

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Forensic Entomology

is not only a useful tool to decide how long human remains have been undetected, but forensic entomology can also be used to find out whether the corpse has been moved after death, the cause of death and also solves cases of contraband trafficking (Catts, 1995).

Forensic entomology can be divided into three categories

 Urban  Store-product  Medicolegal

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Urban

forensic entomology deals with insects that affect man and his immediate environment

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Deals with pest infestations where there might be litigation, for example, landlord and tenants.

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Stored -product

forensic entomology concentrates on commonly found insects in contaminated foods.

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Legal issues on insect infesting stored products

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Medicolegal

, which we primarily focus on, deals with the criminal component of the legal system and with insects that typically infest human remains or corpses.

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Use of insect development and insect colonization to solve crime(s)

Medico-legal Entomology

 Helps determine postmortem interval  Movement of body???

 Determine scene of death  Proves or disproves suspect, witness or corroborating statements regarding death

 http://www.smithsonianchannel.com/site/sn/show.do?episode

=141561  http://www.smithsonianchannel.com/site/sn/show.do?episode

=141561 - measuring-time-with-maggots

Some History

 1200s – Sung Tz’u, a Chinese “death investigator ” uses the behavior of flies to solve a murder. Everyone in the small town where the murder took place is gathered together with their sickles (blades used for cutting grass). Though no obvious blood stains appear on the tools, Tz ’u releases flies into the area which, drawn to the scent of blood, buzz around the murder weapon. The guilty person confesses.

1668- Francesco Redi disproves the theory of spontaneous generation of maggots in rotten meat. The prevailing thought of the day was that maggots appear from nowhere in the spoiled food, as if by magic. His experiment showed that the life cycle of the maggot is associated with the rate of decay, allowing scientists to better estimate a deceased person ’s time of death.

1750s – 1780s – Carolus Linnaeus published a standardized system of biological classification. Scientists use this system to determine the location of a murder, as fly species live in certain habitats.

1855 – Dr. Berger d’Arbois, France’s premier coroner of the day, proves the innocence of residents of a home in which a body is found. By studying fly larvae and mites in the body he determines that they were laid before the body was sealed inside the home of the accused well before the current residents moved in.

1894 – Dr. Jean-Pere Megnin publishes.

The Fauna of Corpses

, describing eight stages of bodily decomposition. Included in these are the types of insects each stage attracts. This further aids scientists in determining a victims time of death and if the body has been moved.

1935 – Dr. Alexander Mearns of Glasgow University uses the development of maggot larvae in a body to determine the victim ’s time of death. This, in conjunction with witness testimony and other evidence, allows a suspect to be convicted in court.

1986 – The first textbook devoted to forensic entomology,

A Manual of Forensic Entomology

, is published. This makes information on this branch of forensics readily available, allowing standardized training for aspiring scientists.

Maggot Mass

Medicolegal Entomology

 Typically focuses on violent crimes  Determination of time of death  Determination of crime scene

A Forensic Entomologist:

 Identifies the immature insects  Determines the size and development of the insects  Calculates the growth of the insects and the stages of the life cycle  Compares the growth against weather conditions to estimate time of ovipositions (egg laying)

Corpse as Insect Food Source

 Bodily decomposition attracts flies  Flies and related insects have highly sensitive olfactory receptor sites on top of head.

 Attracted to protein-rich environment which corpse provides  Insect activity on the corpse within minutes of death  Deposits eggs in natural or unnatural openings, a.k.a., orifices or exposed wounds – eyes, ears, anus, etc.

 Deposits eggs in orifices during daylight

Forensic Entomology

 After the initial decay, and the body begins to smell, different types of insects are attracted to the dead body.  The insects that usually arrives first are the Necrophages, which includes flies (Diptera) such as the blowfly (Calliphoridae) and the flesh flies (Sarcophagidae).

 Blowflies and flesh flies are very important to the forensic entomologist

Calliphorid Flies

 Adult flies can be identified by the iridescent blue, green colors

Sarcophagid Flies

 These flies are grayish with longitudinal dark stripes on the dorsum

Omnivores

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Omnivores, which include wasps, beetles and ants feed on the corpse along with the maggots left by the flies.

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Omnivores may slow the rate of decomposition by decreasing the population of necrophages Parasites and Predators

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Parasites and Predators – beetles and wasps eat immature flies

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Others – spiders, mites, pill bugs and others use the corpse as a source of habitat

Forensic Entomology

   Eggs are laid around the natural orifices such as the nose, eyes, ears, anus, penis and vagina. If the body has wounds the eggs are also laid in such. Flesh flies do not lay eggs, but deposits larvae instead.

Insect Evidence

Some species feed on fresh corpse, while other species prefer to feed on a corpse that has been dead for two weeks.

Investigators also find other insect species that prey on the insects feeding on the corpse. Cleoptera

Forensic Entomology

 The usual sites of oviposition on dead humans are natural openings.  Blowflies will most often lay their eggs in the facial region, and more seldom in the genitoanal region.  If there is a sexual assault prior to death, leading to bleeding in the genitoanal region, blowflies will be more likely to oviposit in these regions.  If there ’s blowfly activity in the genitoanal region, a sexual crime is suggested.

Forensic Entomology

 The sites of blowfly infestation on the corpse may be important in determining the cause of death   For example: if there has been trauma or mutilation of the body prior to death, this may lead to heavy infestation of other body parts than the usual sites when the victim is not mutilated. Under a knife attack, it is usual to guard oneself with arms in front of thorax and head. This may lead to injury on the lower part of the arm. After death, blowfly may oviposit in these wounds.

Blow Fly Life Cycle:

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Eggs

 Laid on a host which is typically dead.

 May be laid within minutes of death.  Eggs typically hatch within 24 hours of depositing

Blow Flies

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Insects are cold-blooded so their development is temperature dependent

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As temperature increases, they develop more rapidly

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As temperature decreases, they develop more slowly

Fly Eggs

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Fly eggs look like parmesan cheese and accumulate in moist areas

Fly Larva

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Eggs hatch within 24 hours after being laid

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Fly larva are also known as maggots

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1 st Instar Stage – 1.8 days (5 mm long)

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The larva will eat until it gets so big it needs to shed its skin

First Instar

 Initially feeds on fluid exuded from the body  Migrates into body  Hatching to first molt takes 1 day

Fly Larva

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2 nd Instar Stage – 2.5 days (10 mm long)

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For another 24 hours these maggots will grow until they shed their skin again

Third Instar

 Still moves in mass  Greatly increases in size  Second molt to pre-pupa takes 2 days

Fly Larva

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3 rd Instar Stage – 4 –5 days (17 mm long)

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Feeding 3 rd instar – maggots are eating Migrating 3 rd instar – maggots stop eating and start moving to the soil under the body

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Maggots are in the 3 rd instar for about 100 hours

Pupa

  Once the maggots are deep within the soil they will go through the pupation in order to become an adult fly.

10 –14 days after oviposition (lay eggs)  Pupa (made of chitin; a hardened protein based substance to protect developing insect that is encased)  Many investigators overlook the dried, hardened outer skin of the larva that is left in the environment when the fly emerges.

PUPA

Fly pupae are often discovered away from the body since maggots migrate. These pupae should be recovered at the death scene if time of death is questionable.

Blow Flies

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Analysis of the oldest insect stage on the body, together with knowledge of the meteorological conditions at the scene, can be used to determine how long insects have been feeding on the body, and hence, how long the victim has been dead

 Almost complete skeletonization of the head by maggots

Young maggots resemble fly eggs but are mobile.

 Fly pupa and other insects present on decedent.

Post-morten ant and roach Activity leaves a typical grouped pattern that looks like an abrasion

Post Mortem Interval

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PMI – time interval from actual death to discovery of the body.

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Cadavers decompose in four stages:

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Fresh Bloated Decay Dry

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Certain insects are attracted to the corpse in each of the four stages of decomposition.

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Succession = the order in which insects are attracted to the decomposing body

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Succession pattern is useful to determine PMI

Post Mortem Interval

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Blowflies are attracted to a fresh corpse in order to lay their eggs

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Carrion flies are attracted to the bloated corpse

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There is a succession database that can be used to estimate PMI

Factors Used to Determine Time Since Death

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4 factors must be taken into account

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Oldest stage of blow fly associated with the body

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Look at old pupal cases

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Species of insects

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Each species develop at different rates so each species of insects at the scene need to be collected

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Temperature data

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Must be able to determine temperature of crime scene for a period of time Developmental data

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Must know how fast or how slow the specific species develop

Degree Hours

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Degrees since death

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The life cycle of the insect is measured by degree-hours because temperature effects the cycle

Calculating PMI from Accumulated Degree Hours (ADH) From Egg To Temp Hours 1 st Instar 70 ° F 23 1 st Instar 2 nd Instar 70 ° F 2 nd Instar 3 rd Instar 70 ° F 3 rd Instar Pupa Pupa 70 ° F Adult Fly 70 ° F 27 22 130 143 ADH 23 x 70= 1610 ADH 27 x 70= 1890 ADH 22 x 70= 1540 ADH 130 x 70= 9100 ADH 143 x 70= 10010 ADH Cumulative ADH 1610 1610+ 1890 1610+1890+ 1540 1610+1890+ 1540+9100 1610+1890+ 1540+9100 +10010

Calculating ADH from Climate Data

Using the Data

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3928 ADH in these three days (952+1488+1488). How many ADH of 70º are there in these 3 days? 3928/70=56.11 hours 72 hours at 70º would have the insects passing to the 3 rd instar. But 72 hours at colder temperatures and insects will only be at 2 nd instar stage.

Determining Whether the Body has been Moved

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Insects present on the deceased body that are not prevalent to the crime scene can indicate that the victim was murdered elsewhere and was dumped at another location

Linking Suspect to Scene

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Sometimes, criminals carry entomological evidence on them unknowingly This evidence can place them at the crime scene by examining the life cycles of the insects

Drugs

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Insects that feed on the body of individuals that have been poisoned can be examined to determine what type of drug or toxin the person was poisoned with

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It is important to note that specific drugs either speed up or slow down larval development

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Can influence entomologist

’

s final report

Forensic Entomology

 • • • • • • • • • • • Analysis of larvae can assist in the identification of drugs used by decedent as well as their DNA •

Triazolam Oxazepam Alimemazine Chloripriamine Phenobarbitol Malathion Mercury Amyltryptiline Nortriptyline Cocaine Phenycyclidine Heroin

Forensic Entomology

 Many of these chemicals will also influence the life-cycle of the maggot.   Cocaine accelerates the development of some sarcophagids. Malathion, an insecticide, is commonly used in suicide, and is usually taken orally.  Amitriptyline, an antidepressant, can prolong the developmental time up to 77 hours, at least in one species of Sarcophagidae.

Collection of Entomological Evidence

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Evidence should be collected by an entomologist

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If not available, a police death investigator should collect the evidence Different stages of larval growth should be collected and bagged separately Sample of soil should also be collected from just outside the area marked by body fluids

Challenges to Forensic Entomology

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3 challenges exist

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Temperature

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Temperature of crime scene and the temperature that the insects have been exposed to us unknown Season

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Entomology is valuable only in spring, summer, and fall Exclusion of insects

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Insects are excluded based on condition of body

Forensic Entomology

 Blow fly pupae were collected from a body found.  The ambient temperature was approximately 75 ° F and the humidity was 20%.  Larva found on the body were approximately 10mm long.  Estimate time since death.

Case Study (Decomposition)

On a hot August day (90 ° F), the body of an elderly man was discovered in a ditch next to a country road. He was lying supine dressed in overalls, a short-sleeved work shirt, and socks without shoes. His abdomen and legs were covered by a blanket. There was marked maggot infestation of the head and neck, partially obscuring a posterior scalp defect, and a ligature around his neck.

Case Study (Decomposition)

The skin of the upper chest, neck, and head were markedly darkened. The rest of the body was not decomposed. There was a slight greenish tinge to the abdominal area. There was no apparent blood on the ground surrounding the victim.

Case Study (Decomposition)

The scalp defect was a four inch gaping laceration with no underlying bone or brain injury. The ligature was a small towel tightly compressing the neck and knotted in the back. There was no rigor mortis and livor mortis was posterior. When the body was turned the livor did not move with gravity.

Case Study (Decomposition)

Stomach contents revealed fragments of sausage pieces, brown liquid and white semi-solid food particles. At least ten maggots were saved in a container of alcohol. The largest maggot was 4mm in length. A diagnosis of ligature strangulation was rendered and the death was ruled a homicide.

Case Study (Decomposition)

 When the wife came in to view his body she made a spontaneous statement, “ I don ’ t understand, he looks fatter than normal.

”

Case Study (Decomposition)

The next day a deputy sheriff called the pathologist to ask about the time of death. The deputy was holding a man in custody who had been seen with the decedent two days before the body was discovered. The suspect claimed that he was out of town the day before the man was found dead. The suspect had a good motive for the murder because of a soured business deal with the victim.

Case Study (Decomposition)

Prior to making a formal arrest, the officer needed to make sure the postmortem interval was consistent with two days. What should the pathologist say about the postmortem interval in this case and why?

Case Study (Decomposition)

One of the most frequently asked questions during death investigation concerns the time of death. Unfortunately, determining the exact time of death from an examination of a body is impossible. Numerous findings must be interpreted to give a reasonable estimation of the postmortem interval. In this particular case, the time of death was key to the arrest because the suspect had an alibi a day before the body was discovered.

Case Study (Decomposition)

In this case, differential decomposition occurred because a head injury caused an open wound. Blood is an excellent source for maggot proliferation, which accelerated the decompositional changes in the head. Since the rest of the body had not decomposed, an estimation of the postmortem interval was made by evaluating the area of least decomposition.

Case Study (Decomposition)

Environmental temperature is the most important factor in determining the rate of decompositional change after death. The decompostional changes in the head and the lack of rigor mortis could occur in 10 to 20 hours in about 90F temperatures. Therefore, in this case the postmortem interval had to be less than 24 hours.

Case Study (Decomposition)

The decedent ’ s stomach contained pieces of sausage, brown liquid and white food particles suggestive of breakfast foods. If he normally ate these foods only in the morning then he probably ate breakfast on the day of his death. Relatives and friends should be contacted to discover a decedent ’ s eating habits to help determine the time of the day he was killed.

Case Study (Decomposition)

Maggot samples were not sent to an entomologist for study because the postmortem interval was sufficiently narrow making this specialized study unnecessary.

Case Study (Decomposition)

The above discussion suggests the decedent died the day before his body was discovered. Therefore, the suspect with the strong alibi did not commit the murder, the investigators need to renew their search for the killer.

Case Study

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The skeletal remains of the buried young girl from Hawaii

Case Study

 The remains of a female child (30 months of age) were recovered from a shallow grave on a narrow ledge on the side of Koko Head Crater, Oahu, Hawaii. The skeletonized remains were buried in dirt and gravel, and some bones were partially exposed. Other bones were scattered on the surface. The skull was facing upward, and the mandible located several feet from the skull. Also present in the grave were four small stuffed dolls.

Case Study

 Examination of the remains at the morgue revealed largely skeletonized material. Present were the skull and mandible, most of the ribs, many thoracic vertebral bodies, the mostly skeletonized pelvis and lower extremities, the left humerus, radius, ulna and scapula. Absent were many of the cervical vertebrae, right upper extremity, and scapula.

Case Study

 Small bones of the left foot appeared to have been chewed and showed signs of postmortem animal depredation, as did the bones of the left forearm. Apparent scalp hair remaining adjacent to the skull was blonde and straight, and measured up to 15 cm in length. Clothing accompanying the remains in which the corpse had been buried

Case Study

 wore a hooded jacket and a pair of running shoes. A second search at the dangerously precarious burial site the day following the recovery of the remains yielded the right scapula and arm as well as additional vertebrae.

Case Study

 Examination of the remains at the morgue yielded a limited assortment of arthropods. Empty puparial cases of the calliphorid Chrysomya rufifacies were attached to the skull under the scalp, which had largely been eaten away. Adult dermestid beetles, Dermestes maculatus,

Case Study

 were present on the bones, and late instar larval skins of that species were observed in areas under the scalp, inside the cranial cavity, and on the femurs. These cast larval skins of D. maculatus were in good condition and did not appear to have been exposed to weathering effects for any period of time. Larval scenopinids (Diptera) were collected from the scull near the bases of the hair.

Case Study

 Adult clerids, Necrobia rufipes, were recovered from the bones of the left foot. A silverfish (Thysanura: Lepismatidae) was recovered from the body bag.

Case Study

 In the hood of the jacket, there was a quantity of soil associated with the remains. This was processed in a Berlese-Tullgren funnel and sorted by hand. This sample yielded additional larval scenopinids and adult D. maculatus There was an adult histerid beetle which represented an undescribed species.

Case Study

 Mites associated with this sample included species in the families Acaridae, Histiostomatidae, Macrochelidae, Pachylaelapidae, ropodidae, and Winterschmidtidae.

Case Study

 Comparison of this assemblage with results of earlier decomposition studies conducted in xerophytic habitats on the island of Oahu resulted in a postmortem interval estimate of 52-76 days. This estimate was lowered to slightly over 52 days, based on the condition of the cast larval skins of D. maculatus. In the decomposition studies used for comparison,

Case Study

 the last observed larval activity for D. maculatus was on day 51. The cast larval skins of D. maculatus disintegrate quite rapidly when exposed to weathering. The fact that these skins were in excellent condition and easily identifiable to species level indicated that they had been shed recently.

Case Study

 The window fly larvae (Scenopinidae) were all late instars and of a size comparable to those collected from decomposition studies on day 51 in one study and day 48 in another study. This tended to reinforce the estimate of slightly over 52 days. The mites recovered also were consistent with this time frame,

Case Study

 and the absence of certain other mite species was indicative of the shorter portion of the computer estimate. The final postmortem interval estimate of slightly over 52 days for this case fit well with the interval established independently by confession of the suspect in this case, the victim's father. Death proved to have occurred in the morning, 53 days prior to the recovery of the remains.

Forensic Entomology

 The exact procedure at the crime scene varies with the type of habitat, but in general we can divide the work of the forensic entomologist in five parts.

1.Visual observation and notations at the scene. 2.Initiation of climatological data collection at the scene.

Forensic Entomology

3.Collection of specimens from the body before body removal. 4.Collection of specimens from the surrounding area (up to 6 m from the body) before removal of the remains. 5.Collection of specimens from directly under and in close proximity to the remains (1 m or less) after the body has been removed.

Forensic Entomology

 Collection of insects and/or maggots  Want to collect bug and fix it so it won ’ t continue to grow.

 Use a ball jar with formalin  Also collect a live specimen with food and let it pupate to the adult species.

 Is it indigenous to the location?

 Use a ball jar with cheese cloth and a rubber band for initial collection purposes.