Forensic Entomology

What is Forensic Entomology? Application of insects to legal issues. Insects associated with crimes Usually violent crimes such as murder, suicide, and rape Physical abuse Insects aid in death investigations by establishing: Timelines - time since death to time of discovery (postmortem interval or PMI) Movement of the corpse, manner and cause of death. Association of suspects with the death scene Detection of toxins or drugs  insect larvae

How do we study entomology? Body Farm

Brief History Sung T’zu (1235) First reference to forensic entomology Bergeret (1855) Use forensic entomology to solve a case of a long-dead infant Megnin (1894) “La Faun des Cadavres: Application l’entomologie a la Medicine Legale” Hall 1948 Monograph on identification of blowflies Nuorteva (1970’s) Rekindled interest in the technique, published series of case histories Keh (1985), Smith (1986), Catts and Goff (1992) Textbooks and reviews

Succession Succession is an ecological term that refers to predictable and orderly changes in an ecological community (in this case, a dead body). A cadaver is a very rich but ephemeral resource There is tremendous competition among organisms, especially in the early stages of decomposition. Insect colonization of a corpse occurs in a series of stages. Different groups are adapted to different stages of a corpse’s decomposition. Thus, there is a fairly predictable sequence of colonization Watch decomposition of a pig

Succession FreshBloated Decay Post-Decay Dry 5555

Living Organism A live pig is not outwardly decomposing, but its intestine contains a diversity of bacteria, protozoans and nematodes. Some of these micro-organisms are ready for a new life, should the pig die and lose its ability to keep them under control.

Fresh Stage (1-2 days PMI) Bacteria begin to digest the intestine from the inside, eventually breaking out of the intestine and digesting other organs. Digestive enzymes and enzymes within cells are released and start to break down the body and break down proteins and carbs into simpler compounds Blowflies begin to lay eggs in the natural openings. These eggs will hatch within a day and maggots will make their way into the body. This stage ends when bloating is first evident.

“Oh my!...What a cute little maggot!”

Fresh Stage Blowflies have detected the cadaver Eggs are being laid, often around the eye, nostrils, mouth, followed by anus or genital openings Eggs

Bloated Stage (2-6 days PMI) Bacteria are releasing fluids into the body. These anaerobic bacteria also produce various gases including hydrogen sulphide, methane, cadaverine and putrescine as by-products. These gases smell disgusting to us, but are very attractive to insects! The build up of gas creates pressure within the body. This pressure inflates the body and forces fluids out of cells and blood vessels and into the body cavity..

Bloated Stage – insect activity Cadaver begins to swell and putrefy Blowflies (calliphora) are still ovipositing Flesh flies (sarcophaga) appear Small maggots are feeding Flesh fly Small maggots Pig’s eye

Decay Stage (Days 5-11) Abdominal wall breaks allowing gasses to escape. Carcass deflates. A large volume of body fluids seep into the soil and other insects feed on this. Several generations of maggots are present in and on the body, some are fully grown. These migrate into the soil where they become pupae.

Decay Stage Adult blowflies no longer attracted. Large masses of maggots feeding externally and internally (MAGGOT MASS)MAGGOT MASS Because of all the metabollic activity, the maggot mass is warmer than the rest of the corpse Predators and parasites of maggots arrive

Post Decay Stage (Days 10-25) All the remaining flesh is removed over this period and the body dries out. It has a cheesy smell, caused by butyric acid, and this smell attracts a new suite of corpse organisms. Beetles feed on the skin and ligaments. The cheese fly consumes any remaining moist flesh at this stage, even though it is uncommon earlier in decay. Predators and parasites are still present at this stage including numerous wasps and beetle larvae.

Post-Decay Stage Cadaver is drying out. Large maggots are leaving or have left

Dry Stage (Days 25+) The body is now dry and decays very slowly. Eventually all the hair disappears leaving the bones only. Animals which can feed on hair include moths, beetles, and micro- organisms like bacteria. Mites, in turn, feed on these micro-organisms.

Dry Stage Skin and bones Insects with the ability to digest keratin (clothes moths and dermestid beetles).

Major Groups of Insects Associated with Cadavers Flies Blowflies Flesh Flies House Flies Cheese Skippers Beetles Carrion Beetles Dermestids

The first flies! Blow flies (Calliphora) and House flies (Musca) are the first flies to arrive.

Then come the … Flesh flies (sarcophaga) come later by they lay live larvae so this keeps them competitive with the earlier colonizers.

And even later come the … Cheese flies (Piophila) who are attracted to the cheesy odor that emanates from the corpse during the later stages of decomposition.

Much much later … Coffin flies are most active on a dry corpse and are unique in that they can dig their way through cracks in the soil above buried corpses. They can also complete their entire life cycle underground.

The Beetles Not these BEATLES!

These beetles! Dermestid beetles feed on dried skin, ligaments, tendons, bone left by fly larvae. Ham beetles feed on dried fat. Carrion beetles feed on maggots.

Moths Clothes moths feed on hair and nails (contain keratin)

Post-Mortem Interval (PMI) Elapsed time from a death to the discovery of a cadaver. Flies (especially calliphorids and sarcophagids) can be vital in determining the PMI Premises Flies will begin oviposition as soon as they discover a body Succession on a corpse is predictable Insect development is predictable

Fly development Fly development is structured into stages Each stage requires a certain amount of time Time to complete a stage is temperature dependent. At warmer temperatures the rate of development is fast, at cool temperatures it slows down Each species has a certain developmental rate at any given temperature Presence of drugs in the body can also affect the rate of development.

Determining the PMI Step 1. Collect samples of the insects present. Critical to collect the largest maggots on the cadaver, even if they are few. Representative samples of other maggots present. Preserve some immediately. Rear others to adulthood to confirm species ID’s Step 2. Determine temperature history at crime scene Air temperature for general area (airport readings, validate with micro data-loggers). Look for ‘windows’ of insect opportunity Determine if there are any drugs present in the body. Step 3. Estimate time of egg laying Given the species present and their age (size), how long did it take them to develop to that point at the temperatures occurring in the area. Step 4. What other insect evidence is available? Look for other insect evidence that might corroborate or contradict your PMI estimate.

Put it all together … Looking at all the information together one can predict the estimated date of death. Now we will try with “Of Maggots and Murder” Muahahahahahahahaha …