Under The Microscope: Insects In Medico-Criminal Investigations

  

The use of insects in medico-criminal investigations enjoys a long practice. The oldest reported case dates to 1235 A.D. in China when a local “Death Investigator” determined that the presence of adult flies on the washed sickle confirmed the guilt of a murder suspect, who subsequently confessed to the crime. Among law enforcement practitioners, maggots and other insects have traditionally been regarded as unpalatable byproducts of the decomposition process. The sights and smells of a heavily infested corpse can be very disturbing, and these invaders are often looked upon as pests. These pests are often washed down the autopsy table with little regard to their evidentiary value. The challenge to investigators is to realize that insects can be our partners in solving crime. Their presence on a corpse can provide valuable information not attainable from any other source. Forensic entomologists may offer a variety of analyses in both criminal and civil matters, they are most often called upon to examine insects recovered from deceased individuals. Following death, a corpse can be quickly colonized by a variety of necrophagous and saprophagous arthropods, especially insects. This faunal succession of invertebrates also includes parasitic and predacious species of the necrophagous insects, omnivorous species which feed on the corpse and invading insects, and adventive species which may utilize the corpse as a temporary habitat. This faunal succession is a valuable phenomenon to entomologists, as it often assists them in understanding the history of the corpse. As each species of insect arrives and feeds on the body, they invariably change the corpse, thereby making it attractive to the next group of insects. The lines separating these successional waves are far from distinct, as environmental and biological systems vary from location to location.

 

During warm months, flies (Diptera) are the main decomposers, and are the major invertebrate fauna on carrion. Adult flies of the families Calliphoridae (blow flies) and Sarcophagidae (flesh flies) may arrive within a few minutes after death. After locating on a corpse, gravid females will then laytheir eggs (Calliphoridae) or larvae (Sarcophagidae). Usually these species favor the natural orifices but may also be preferentially attracted to sites of trauma such as gunshot injuries, sharp force, and blunt force trauma. These flies undergo what is known as holometabolous, or complete, metamorphosis. There are three larval growth stages called instars which are each separated by a molting. This is followed by a wandering phase and then the pre-pupal and pupal stage. The pupal stage is easily recognized as the outer skin darkens to a reddish brown to black color with the developing pupa inside. These pupae can be found in the soil, adjacent leaf litter, or clothing of the victim. The pupae are immobile and assume a barrel shape, similar in appearance to rodent droppings. After development, the adult fly will emerge, leaving the durable puparium behind. The stage of development of the larvae (maggots) of these flies is the most reliable indicator for estimating what has traditionally been referred to as the time since death, or post mortem interval. Entomologists have been studying these rates of development for different species and have established

reliable data on how quickly each stage develops under varying temperatures. For example, once the adult female fly deposits her clutch, a kind of biological stop watch is started. Once the species and the stage of development is established, the entomologist can then review the temperature data from the crime scene and determine how long it would have taken the maggots to reach the observed stage of development. There is agreement among entomologists that the longer a corpse has been exposed, the less precise the estimate will be, although this is not always the case. This time frame is commonly referred to as the post mortem interval, or time since death. This is a familiar term in death investigations, and caution is warranted in its use in entomology, as “time estimate” is not actually measuring the time since the victim died. Rather, entomologists are measuring the time since the corpse was first colonized by the insects analyzed. While this difference may seem trivial, there is sound reasoning for the distinction.

 

While flies may locate on a corpse immediately following death — often within minutes — and begin oviposition or larviposition, there are a variety of biological, situational, and environmental factors which could hinder the arrival of adult flies. Temperature and humidity are by far the most influential environmental factors. Generally, adult flies will not be active in flight when ambient air temperatures fall below 10°C. It follows that a corpse dumped in a field during a period of cold temperatures will not immediately be colonized by these species — even though death has occurred. Likewise, concealment (temporary or prolonged) of the corpse by means of burial or placement in a location inaccessible to adult insects (e.g., metal drum, car trunk, water) will also retard or prevent this “clock” from starting. Additionally, once the corpse is physically accessible by adult flies, it may have advanced to a stage of decomposition that is unattractive to adult flies and unsuitable for maggot development. The degree to which these factors influence a particular analysis must be determined on a case by case basis. Failure to consider these factors could lead to a serious error in the estimate of time

since colonization. Furthermore, use of the term “time since death” can cause a misunderstanding by law enforcement personnel unless clarification is made by the entomologist as to whether he actually believes that colonization occurred immediately following death.

 

 

 

 

 

Acknowledgements:

www.aived.nl    AIVD ©

Algemene Bestuursdienst – @Erik Akerboom ©

www.politie.nl  Politiekorpschef  @Janny Knol©

www.politie.nl WEB Politie - @Henk van Essen©

 

Bibliography:

 

1.    Criminal Investigations – Crime Scene Investigation.2000

2.    Forensic Science.2006

3.    Techniques of Crime Scene Investigation.2012

4.    Forensics Pathology.2001

5.    Pathology.2005

6.    Forensic DNA Technology (Lewis Publishers,New York, 1991).

7.    The Examination and Typing of Bloodstains in the Crime Laboratory (U.S. Department of Justice, Washington, D.C., 1971).

8.    „A Short History of the Polymerase Chain Reaction". PCR Protocols. Methods in Molecular Biology.

9.    Molecular Cloning: A Laboratory Manual (3rd ed.). Cold Spring Harbor,N.Y.: Cold Spring Harbor Laboratory Press.2001

10.   "Antibodies as Thermolabile Switches: High Temperature Triggering for the Polymerase Chain Reaction". Bio/Technology.1994

11.   Forensic Science Handbook, vol. III (Regents/Prentice Hall, Englewood Cliffs, NJ, 1993).

12.   "Thermostable DNA Polymerases for a Wide Spectrum of Applications: Comparison of a Robust Hybrid TopoTaq to other enzymes". In Kieleczawa J. DNA Sequencing II: Optimizing Preparation and Cleanup. Jones and Bartlett. 2006

13.   Nielsen B, et al., Acute and adaptive responses in humans to exercise in a warm, humid environment, Eur J Physiol 1997

14.   Molnar GW, Survival of hypothermia by men immersed in the ocean. JAMA 1946

15.   Paton BC, Accidental hypothermia. Pharmacol Ther 1983

16.   Simpson K, Exposure to cold-starvation and neglect, in Simpson K (Ed): Modem Trends in Forensic Medicine. St Louis, MO, Mosby Co, 1953.

17.   Fitzgerald FT, Hypoglycemia and accidental hypothermia in an alcoholic population. West J Med 1980

18.   Stoner HB et al., Metabolic aspects of hypothermia in the elderly. Clin Sci 1980

19.   MacGregor DC et al., The effects of ether, ethanol, propanol and butanol on tolerance to deep hypothermia. Dis Chest 1966

20.   Cooper KE, Hunter AR, and Keatinge WR, Accidental hypothermia. Int Anesthesia Clin 1964

21.   Keatinge WR. The effects of subcutaneous fat and of previous exposure to cold on the body temperature, peripheral blood flow and metabolic rate of men in cold water. J Physiol 1960

22.   Sloan REG and Keatinge WR, Cooling rates of young people swimming in cold water. J Appl Physiol 1973

23.   Keatinge WR, Role of cold and immersion accidents. In Adam JM (Ed) Hypothermia – Ashore and Afloat. 1981, Chapter 4, Aberdeen Univ. Press, GB.

24.   Keatinge WR and Evans M, The respiratory and cardiovascular responses to immersion in cold and warm water. QJ Exp Physiol 1961

25.   Keatinge WR and Nadel JA, Immediate respiratory response to sudden cooling of the skin. J Appl Physiol 1965

26.   Golden F. St C. and Hurvey GR, The “After Drop” and death after rescue from immersion in cold water. In Adam JM (Ed). Hypothermia – Ashore and Afloat, Chapter 5, Aberdeen Univ. Press, GB 1981.

27.   Burton AC and Bazett HC, Study of average temperature of tissue, of exchange of heat and vasomotor responses in man by means of bath coloremeter. Am J Physiol 1936

28.   Adam JM, Cold Weather: Its characteristics, dangers and assessment, In Adam JM (Ed).Hypothermia – Ashore and Afloat, Aberdeen Univ. Press, GB1981.

29.   Modell JH and Davis JH, Electrolyte changes in human drowning victims.Anesthesiology 1969

30.   Bolte RG, et al., The use of extracorporeal rewarming in a child submerged for 66 minutes. JAMA 1988

31.   Ornato JP, The resuscitation of near-drowning victims. JAMA 1986

32.   Conn AW and Barker CA: Fresh water drowning and near-drowning — An update.1984;

33.   Reh H, On the early postmortem course of “washerwoman’s skin at the fingertips.” Z Rechtsmed 1984

34.   Gonzales TA, Vance M, Helpern M, Legal Medicine and Toxicology. New York, Appleton-Century Co, 1937.

35.   Peabody AJ, Diatoms and drowning – A review, Med Sci Law 1980

36.   Foged N, Diatoms and drowning — Once more.Forens Sci Int 1983

37.   "Microscale chaotic advection enables robust convective DNA replication.". Analytical Chemistry. 2013

38.   Sourcebook in Forensic Serology, Immunology, and Biochemistry (U.S. Department of Justice, National Institute of Justice, Washington, D.C.,1983).

39.   C. A. Villee et al., Biology (Saunders College Publishing, Philadelphia, 2nd ed.,1989).

40.   Molecular Biology of the Gene (Benjamin/Cummings Publishing Company, Menlo Park, CA, 4th ed., 1987).

41.   Molecular Evolutionary Genetics (Plenum Press, New York,1985).

42.   Human Physiology. An Integrate. 2016

43.   Dumas JL and Walker N, Bilateral scapular fractures secondary to electrical shock. Arch. Orthopaed & Trauma Surg, 1992; 111(5)

44.   Stueland DT, et al., Bilateral humeral fractures from electrically induced muscular spasm. J. of Emerg. Med. 1989

45.   Shaheen MA and Sabet NA, Bilateral simultaneous fracture of the femoral neck following electrical shock. Injury. 1984

46.   Rajam KH, et al., Fracture of vertebral bodies caused by accidental electric shock. J. Indian Med Assoc. 1976

47.   Wright RK, Broisz HG, and Shuman M, The investigation of electrical injuries and deaths. Presented at the meeting of the American Academy of Forensic Science, Reno, NV, February 2000

48. Broor SL, Kumar A, Chari ST, et al. 1989. Corrosive oesophageal strictures following acid ingestion: clinical profile and results of endoscopic dilatation.

49. Baud FJ, Barriot P, TOGS V, et al. 199 1. Elevated blood cyanide concentrations in victims of smoke inhalation.

50. Blackwell M, Robbins A. 1979. Arsine (arsenic hydride) poisoning in the workplace