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Saturday, 9 June 2012

something from the postgrad days

Entomology Research Project (research so far)

From research so far the main uses of forensic entomology are as follows;

Ø  Determination of time of death.
Ø  Determination of any illicit substances taken by the deceased.
Ø  Sites of injury and any sexual assault.
Ø  Location of death and whether body has been moved.
Ø  Other uses not linked to death include, food tampering, bite marks and hygiene issues. (which I’m not that interested in)

Injury sites
With regard sites of injury and presence of sexual assault, this is mainly due to insect laying habits. Insects tend to lay eggs (occasionally live birth) as close to breaks in the skin as possible. Regular laying sites tend to be around the face as this is likely to be exposed. On the face the corners of the eyes or just under the eye-lids, corners of the mouth, ears and nasal passages are the common places for laying. However in the case of a sexual assault it is noted that the groin area will receive much more insect attention than the face, in fact in some cases it has been noted that the face is neglected in favour of the vagina. The same can be said for wounds on a corpse. Gunshot trauma or other serious injury tends to be common sites for insect laying. This is due to the area being open flesh which is a preferable site as it gives the larvae a relatively easy route into the bulk of the rotting flesh.

The problem however is that investigating this occurrence without using actual cases would be difficult as any experiments running this would pose serious obstacles. It would require the test animal (most likely a pig) to have been wounded before its death or for it to have been violated. Both of which would be difficult achieve and also an ethically a tricky area to circumnavigate. Therefore this area of forensic entomology is not suited to a summer research project, unless the research was to review prior cases and draw conclusions.

Movement of a body
Location of death sites and showing if a body had been moved can be shown by the insects found upon the corpse. Certain species of blow fly only breed in specific areas (the difference between urban and rural species). If a body is killed in an urban area there are chances that flies from that location will lay eggs or have visited the body prior to it being deposited in for instance a rural area where it is left to be visited by the local rural fauna. This can also work for species of insect which are land based and find their way onto a body which is found submersed in water. While this can help narrow down the location that a body originated (and help locate the primary crime scene) it is not specific to certain areas.

There is scope for investigating specific fauna in areas and also showing how long a dead body needs to be left in for example a house on a hot summers day before flies are attracted to it, which could help show how long prior to movement a body had been left. This is an area to think about which could be tested although the it would be fairly specific for the locations used and the climactic conditions present at that time.

Illicit substances present in the deceased

This can be determined firstly by the location and size of the maggots of a similar age to other ones on the same body. This is typically true of ‘super maggots’ found in the nasal cavities of cocaine users. However as maggots feed upon the flesh of the deceased what drugs were in the deceased the present themselves in the maggots, so a toxicology screening of the tissue as well as the stomach contents of the maggots will show which substances are present.

While there is scope for experimentation in this area, feeding pigs cocaine or heroin in order to run the tests post mortem is ethically a very difficult area. This again is an area which is best suited to research based upon actual samples from cases.

Time of death studies

This is possibly they most common use for forensic entomology. Time of death is normally difficult to predict via medical means (liver temperature etc) after 72hours. For these cases the age of insects on the body and the number and species of insects (succession can occur on bodies left for prolonged periods) as well as the temperature and location of the body can all be used to determine the time of death.

This is where there is a lot of scope for research based investigation. Knowing where a body is and which insects it attracts and which insects follow in succession for different areas and climactic conditions could be investigated. As well as the effects of locking a body in a car or house of burying it, then of course it would take insects longer to get to the body. The nature of the internship of the body would also be interesting if it was buried. How well is it buried and what materials are used (coffin against shallow grave). 

Other areas within this to consider are the effects of different events upon the insect communities and how they react to those events. For instance if a body was in a house fire (either to hide the body or the death was due to the fire) will insects artifacts have survived the fire or after the fire will the body still draw insects (for extreme cases where a body has not been discovered following a fire.

In a similar vein if a body is dumped into a body of water what effect will this have on its insect population? If there is any insects before the body is dumped, if not will the body still attract insects, is this dependant on the type of water (pond, river etc) or the depth, (terrestrial species getting to a body part near the surface or aquatic species to a body under the water).

It is these final to areas that I would be interested in researching as I feel that not only would the experiments be feasible but also that the conclusions which could be drawn would have great use in this field. Although it would not be possible to investigate all the areas, the fire angle may be slightly easier to investigate as it would not require finding an area of water which is guaranteed to be undisturbed by passers by. However burying pig bodies in different settings and conditions may be easier to perform than finding a suitable area to ‘mock up’ a house fire.

Further research is still being preformed but this is the stage that my thinking has got too hopefully my ideas are feasable. In terms of details and specific research papers I am still looking (not having access to the forensic science database off campus doesn’t help!).

Chris Gibson

Some of the literature I have read so far;

Chapter 18; the application of entomology to criminal investigations. J. F.Wallman 2004

Chapter 27; on the body: insects’ life stage presence and their postmortem artifacts. N.H. Haskell, R.D. Hall, V.J. Cervenka and M.A. Clark. 1997

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