how flies can be used in a crime scene investigation?

Question

dont give me links...
give me some paragraphs...
-estimate the time of the death
-the cause of the death

Answer 1

The term is Forensic Entomology. This is far too extensive to detail.

There are currently about 700,000 described species and it is estimated that there may be more than 10 million species of insects yet to be described. Some insects have evolved a gradual or "paurometabolous" development in which there is an egg that hatches into an immature or "nymph", which resembles the adult form, but is smaller and lacks wings. In the forensically important insects, this is best represented by the cockroaches. However, most forensically important insects undergo a complete or "holometabolous" development. There is an egg stage (except for a few insects such as the flesh flies that deposit living larvae) which hatches into a larval form and undergoes a stepwise or incremental growth. This pattern is caused by the successive molts (shedding of the outer skin that has become too small) that the larva must undergo before it finally enters the inactive pupal stage. The pupa is simply the hardened outer skin of the last larval stage and the adult will develop inside of this protective skin.

Blow flies

In the insects that undergo complete development, the larval stages appear quite different from the adult form. The larvae of flies (order Diptera) that are commonly recovered from decomposing human remains lack functional legs, and the body of many species appears cream colored, soft-bodied, and quite "maggot-like". Once the larva or "maggot" is through feeding it will migrate away from the corpse in order to find a suitable site to form the pupal stage. The pupae of blow flies are often overlooked, as they closely resemble rat droppings or the egg case of cockroaches. The pupal stage is an extremely important stage to the forensic entomologist and a thorough search should be made for the presence of pupae at any death scene. If the adult insect has not emerged, the pupa will appear featureless and rounded on both ends. If the adult insect has emerged, one end will appear as if it has been cut off, and the hollow interior will be revealed. Most adult blow flies appear a metallic green or blue and are easily recognizable.


Beetles

The beetles (order Coleoptera) are one of the largest groups of animals and they also undergo complete development. Because of their development the larvae appear very different from the adult form. Although the larvae or "maggots" of a large number of blow fly species may look almost identical; the larvae of beetles may look very different from one species to the next. Beetle larvae recovered from corpses can be easily differentiated from maggots as they have 3 pairs of legs and the maggots found on decomposing remains will not have any legs. Once a larva as been identified as that of a beetle, further field identification can be accomplished because of the wide diversity of larval forms. The bodies of beetle larvae may range from almost white, robust, and hairless to dark brown, slender, and quite hairy. Others may appear almost black and have armored plates on their back.

Death Scene Procedures:

It is important to note that the collection of insects and other arthropods from a death scene may disturb the remains. Therefore, the forensic entomologist (or the crime scene personnel charged with making the collection) should contact the primary investigator and make plans for the collection of entomological evidence. Once a course of action as been determined, utmost care should be taken during insect collection so that the remains are disturbed as little as possible. Before collections are made notes should be taken as to the general habitat, ambient weather conditions, and location of the body. Observations should also be made to describe the microhabitat immediately surrounding the body.

Scene observations and weather data.

Entomological investigation of the death scene can be broken down into the following steps ( detailed in Entomology and Death: A Procedural Guide, E. P. Catts and N. H. Haskell [eds.]).

1). Observations of the scene should note the general habitat and location of the body in reference to vegetation, sun or shade conditions, and its proximity to any open doors or windows if recovered within a structure. Locations of insect infestations on the body should be documented as well as noting what stages of insects are observed (such as eggs, larvae, pupae, or adults). It is also useful to document evidence of scavenging from vertebrate animals and predation of eggs and larvae by other insects such as fire ants. Observations such as these can be noted on the Death Scene Form.

2). Collection of climatological data at the scene. Such data should include:

a). Ambient air temperature at the scene taken approximately at chest height with the thermometer in the shade. DO NOT EXPOSE THERMOMETER TO DIRECT SUNLIGHT!

b). Maggot mass temperature (obtained by placing the thermometer directly into the larval mass center).

c). Ground surface temperature.

d). Temperature at the interface of the body and ground (simply place the thermometer between the two surfaces).

e). Temperature of the soil directly under the body (taken immediately after body removal).

f). Weather data that includes the maximum and minimum daily temperature and rainfall for a period spanning 1-2 weeks before the victims disappearance to 3-5 days after the body was discovered. Such information can be gathered by contacting the nearest national weather service office, or your state climatologist.

Collection of insects from the body at the scene

The first insects that should be collected are the adult flies and beetles. These insects are fast moving and can leave the crime scene rapidly once disturbed. The adult flies can be trapped with an insect net available from most biological supply houses. They are inexpensive and readily obtainable. Once the adult flies have been netted, the closed end of the net (with the insects inside) can be placed in the mouth of a "killing jar" (which is a glass container with cottonballs or plaster soaked with ethyl acetate, or common fingernail polish remover). The jar is then capped and the insects will be immobilized within a few minutes. Once they are immobile they can be easily transferred to a vial of 75% ethyl alcohol. Beetles can be collected with forceps or gloved fingers and placed directly into 75% ethyl alcohol.

It is extremely important that the collected specimens are properly labeled. Labels should be made with a dark graphite pencil, NOT IN INK. The label should be placed in the alcohol along with the specimens, and alcohol can dissolve the ink from the paper! However, pencil is not affected by alcohol and should be used for labeling purposes. The collection label should contain the following information:

1). Geographical Location

2). Date and hour of collection

3). Case number

4). Location on the body where removed

5). Name of collector

**A duplicate label should be made and affixed to the exterior of the vial.**

Once the adults have been collected the collection of larval specimens from the body can begin. First the investigator should search for the presence of eggs, which are easily overlooked. After this step, the larvae should be readily apparent on the body. Generally speaking, the largest larvae should be actively searched for and collected. Additionally, a representative sample of 50-60 larvae should be collected from the maggot mass. These insects can be placed directly into a killing solution or ethyl alcohol. However, the specimens are better preserved if they are placed in boiling water for about 30 seconds. Obtaining boiling water at a scene is difficult, so boiling of the larvae upon returning to the proper facility is satisfactory. If the larvae are boiled with about 48 hours of initial preservation, a good specimen should result. It is important to note that some forensic entomologists prefer not to have the submitted larvae boiled. Therefore, the investigator should discuss preservation techniques with their cooperating entomologist. In any case the exact preservation techniques should be documented and forwarded to the forensic entomologist. If the body has more than one area of colonization (more than one maggot mass) each site should be treated separately.

Once the preserved collections have been made, duplicate samples should be made for live shipment. Living specimens can be placed in specimen containers or Styrofoam cups with tight fitting lids along with some moist paper toweling, or most preferably a food substrate such as beef liver or pork meat. Tiny air holes should be poked in the lid using an ice pick or similar instrument. This cup should be placed into a slightly larger container that has about 1/2 inch of soil or vermiculite in the bottom to absorb any liquids that may accumulate and leak. This entire container should be enclosed in an appropriate shipping container and shipped overnight to a forensic entomologist.

Collection of insects from scene after body removal

Many of the insects that inhabit a corpse will remain on, or buried, in the ground after the body has been removed. The steps listed above should be followed when collecting insects from the soil (i.e. both a preserved and a living sample should be taken). Soil and litter samples should also be taken both immediately under where the body was positioned, and from the immediate surroundings. It is not necessary to dig deeply. A good technique is to collect the leaf litter and debris down to the exposed upper surface of the soil, and then make a separate collection from about the first two or three inches of topsoil. Each soil collection area should be about 4-6 inches square, and be taken from underneath the head, torso and extremities. All soil samples should be placed in a cardboard container for immediate shipment to a forensic entomologist. These collections should be labeled and forwarded to the forensic entomologist along with the insects collected from the body.

Flies are often first on the scene. They prefer a moist corpse for the maggots to feed on, as such a corpse is easier for them to chew. The most important families are:

Blowflies - Family Calliphoridae
Fleshflies - Family Sarcophagidae
House Flies - Family Muscidae
Cheese Flies - Family Piophilidae
Coffin Flies - Family Phoridae
Lesser Corpse Flies - Family Sphaeroceridae
Lesser House Flies - Family Fanniidae
Black scavenger flies - Sepsidae
Sun Flies- Heleomyzidae
Black soldier fly- Stratiomyidae

Beetles are generally found on the corpse when it is more decomposed. In drier conditions, the beetles can be replaced by moth flies (Psychodidae).

Rove Beetles - Family Staphylinidae - are elongate beetles with small elytra (wing covers) and large jaws. Like other beetles inhabiting carrion, they have fast larval development with only three larval stages. Creophilus species are common predators of carrion, and since they are large, are a very visible component of the fauna of corpses. Some adult Staphylinidae are early visitors to a corpse, feeding on larvae of all species of fly, including the later predatory fly larvae. They lay their eggs in the corpse, and the emerging larvae are also predators. Some species have a long development time in the egg, and are common only during the later stages of decomposition. Staphylinids can also tear open the pupal cases of flies, to sustain themselves at a corpse for long periods.

Hister Beetles - Family Histeridae. Adult histerids are usually shiny beetles (black or metallic-green) which have an introverted head. The carrion-feeding species only become active at night when they enter the maggot-infested part of the corpse to capture and devour their maggot prey. During daylight they hide under the corpse unless it is sufficiently decayed to enable them to hide inside it. They have fast larval development with only two larval stages. Among the first beetles to arrive at a corpse are Histeridae of the genus Saprinus. Saprinus adults feed on both the larvae and pupae of blowflies, although some have a preference for fresh pupae. The adults lay their eggs in the corpse, inhabiting it in the later stages of decay.
Carrion Beetles - Family Silphidae
Ham Beetles - Family Cleridae
Carcass Beetles - Family Trogidae
Skin/Hide Beetles - Family Dermestidae. Hide beetles are important in the final stages of decomposition of a carcass. The adults and larvae, which are hairy, feed on the dried skin, tendons and bone left by fly larvae. Hide beetles are the only beetle with the enzymes necessary for breaking down keratin, a protein component of hair.
Scarab Beetles - Family Scarabaeidae
Sap beetles - Family Nitidulidae

Many mites feed on a corpse. Macrocheles mites are common in the early stages of decomposition, while Tyroglyphidae and Oribatidae mites such as Rostrozetes feed on dry skin in the later stages of decomposition.

Nicrophorus beetles often carry on their bodies the mite Poecilochirus which feeds on fly eggs. If they arrive at the corpse before any fly eggs hatch into maggots, the first eggs are eaten and maggot development is delayed. This may lead to incorrect PMI estimate. Nicrophorus beetles find the ammonia excretions of blowfly maggots toxic, and the Poecilochirusmites, by keeping the maggot population low, allow Nicrophorus to occupy the corpse.

Clothes-moths - Family Tineidae - feed on mammalian hair during their larval stages and may forage on any hair that remains. They are amongst the final animals contributing to the decomposition of a corpse.

The insects in this group, order Hymenoptera, are not necessarily necrophagous. While some feed on the body, some are also predatory, and eat the insects feeding on the body. Bees and wasps have been seen feeding on the body during the early stages. This may cause problems for murder cases in which larval flies are used to estimate the post mortem interval since eggs and larvae on the body may have been consumed prior to the arrival on scene of investigators.

Wasps – (particularly) Family Vespidae
Ants – Family Formicidae
Bees - Superfamily Apoidea

Within minutes after death, a fly will often show up, either to eat some protein-rich liquid, or to lay the eggs. As a body decays, it emits various chemicals with names such as "cadaverine" and "putrescine". They float away from the body and can be smelled (by a fly) up from over a kilometre away. As the ratio of the various different chemicals changes after death, different waves of insects come to invade the body. After the flies, come the ants - to eat the fly eggs. Beetles will eat the fly eggs after they've turned into maggots, and sometimes wasps will lay eggs in the maggot mass. Carrion beetles will chew off the flesh, inject an egg into it, and then bury it underground. And at the end, common clothes moths and beetles will strip off everything that isn't bone.

The maggots make strange things happen to the body. They eat the flesh, and turn it into maggots. Around the second week, if you accidentally stumble against the corpse, all the maggots will move at the same time, and the body will appear to jump. Around day 19 after the maggots hatch, they will all leave the corpse, which can quite rapidly lose up to 90% of its weight!

If you know the time-table of the to-ing and fro-ing of the different insects, you can work out the time of death. But this field of forensic entomology is a complicated one. For example, drugs in the body of the victim will change the rate at which different waves of insects come. As a further complication, the insects of cities are different to those that live in rural areas. If insect samples have been collected properly, and noted the weather conditions and the amount of shade on a body and so on, the forensic entomologists can tell the time of death to within six hours or so.

The lifecycle of a fly

Eggs
present in clumps of up to 300
laying to hatching takes 1 day

Larva - 1st instar

initially feeds on fluid exuded from the body
migrates into body
hatching to first moult takes 1 day

Larva - 2nd instar

moves around in maggot mass
first moult to second moult takes 1 day

Larva - 3rd instar

still moves in mass
greatly increases in size
second moult to pre-pupa takes 2 days

Pre-pupa

migrates away from the corpse seeking a suitable pupation site, (usually in soil)
does not feed
transforms into pupa
pre-pupa to pupa takes 4 days

Pupa

resides within puparium
undergoes transformation from larval body form adult fly
does not feed
pupa to emergence takes 10 days

Adult fly

mates on emergence from pupa
feeds on protein from body fluids
lays eggs on corpse
emergence to egg laying takes 2 days
These development times are generalised. They vary depending on the species and the temperature.

I could go on but I still would not be able to answer your question, its not a matter of being 1 or 2 days its a complex analysis of many factors including the insects present. Weather pattern is equally important.

Hope I have been of some help.

Answer 2

Hrmmmm, interesting. Lets see if we can work this out. According to quick research, the common housefly lives for approximately 30 days. That means we may be dealing with an undisturbed crime scene with dead, dying, and flying houseflies.

Other ideas include, the housefly is trapped between the window and the outside screen. Closer examination of the fly shows it's feet are covered with a solution that was only present during the time of the "incident." You could even have a housefly in the fridge or other closed environment (oven?). As for manner of death ...

A body could land with a thump, upon an unsuspecting housefly, and crush it into the table. A housefly could simply be splattered against the wall (by hand, by swatter). A housefly could be floating in a mixed drink. A housefly could be sprayed with bug killer (which was also used as the murder weapon). A housefly could be frazzled on a green/red light bug killer. Finally, the housefly could be found in someone's mouth (by pure accident, but causing the investigators some serious red-herring concern over how it got there). Enjoy.

Answer 3

...through flies a dead body in a crime investigation can be found..it can tell us wether the dead human body is already dead for how many hours or how long it was there already........