Problems in Estimation of Postmortem Interval Resulting from Wrapping of the Corpse:

A Case Study from Hawaii'

M. Lee Goff

Dept. of Entomology 3050 Maile Way

University of Hawaii at. Manoa Honolulu, Hawaii 96822

J. Agric. Entomol. 9(4):237·243 (October 1992)

ABSTRACT The remains of a female were discovered on the island of Oahu, Hawaiian Islands, wrapped in two layers of blankets. The Diptera recovered from the remains indicated a postmortem interval of 10.5 d. based on developmental rates for two species of Calliphoridae: Chrysomya mega­cephala (Fabricius> and Chrysomya rufifacies (Macquart). It was experimen­tally determined that the wrapping of the remains in blankets delayed inva­sion of the remains for oviposition by flies by 2.5 d, thus resulting in a final postmortem interval estimate of 13 d. This estimate was consistent with the circumstances of the case, as the victim had last been seen alive during the afternoon 14 d prior to discovery of the remains.

KEY WORDS Forensic entomology, postmortem interval, Diptera, Calliphori­dae, ADH, developmental rates, barriers.

During the past several years, there has been a renewed interest on the part of entomologists, medical examiners, and law enforcement agencies in the tech­niques for estimation of postmortem intervals using entomological evidence. This renewed interest has resulted in publication of a number of baseline stud­ies detailing the roles of insects in the decomposition process (Early and Goff 1986, Tullis and Goff 1987), basic biological and systematic studies on taxa involved in the decomposition process (Erzinclioglu 1985a, Baumgartner and Greenberg 1986, Braack and Retief 1986, Liu and Greenberg 1989, Goodbrod and Goff 1990), and case studies (Greenberg 1985, Lord et al. 1986, Goff and Odom 1987, Goff et al. 1988, Hawley et al. 1989). To a large extent, these pub­lished case studies have detailed methodologies for estimation of the post­mortem interval for remains which have been readily available for insect colo­nization either inside of dwellings or out of doors. Few published cases have dealt with situations in which the insects are prevented from accessing remains readily due to barriers, such as plastic or cloth wrappings or burial. There has been some experimental work on decomposition of buried remains by Rodriguez and Bass (1985). Nuorteva (l977) detailed a case in Finland in which covering of the remains with a polyethylene sheet served to delay colonization by flies for 4-5 d, and another in which a thin layer of soil had delayed oviposition by 7 d.

I Received for publicat.ion 10 January 1991; accepted 29 March 1991.

237

238 J. Agric. Entomol. Vol. 9, No.4 (1992)

Erzinclioglu (l985b) reported a case in which the remains had been wrapped in a blanket, which served to delay insect colonization. The case reported here demonstrates the effect of wrapping remains in layers of blankets on the ovipo­sition by Calliphoridae on the island of Oahu, Hawaii.

Case Study

The remains of a 32-yr-old female were discovered by searchers in a brushy area near Kahuku on the north shore of Oahu at ca. 1400 h on 31 December 1989. The remains wcr"c wrapped in two layers of blankets and securely tied with an elastic bandage (Fig. 1). There were a large number of adult Calliphori­dae present in the area surrounding the remains and on the blankets enclosing the remains. These flies represented three species commonly associated with decomposing remains on the island of Oahu (GolT et al. 1986): Chrysomya mega­cephala (Fabricius), ChrysOl1tya rufifacies (Macquart), and Phaenicia cuprina (Wiedemann). Specimens of these flies were collected prior to removal of the blankets from the remains. On the outer surface of the blankets, there were egg masses of Diptera along with puparia of both C. megacephala and C. rufi[acies. An adult histerid, Saprinus ill-gens Erichson, was also collected from the outside of the blankets. As the blankets were unwrapped, a centipede, Scolpendra sub­spinipes Leach, was observed preying on maggots. Numerous puparia of both C. megacephaia and C. rufifacies were present between the folds of the blankets. Physically, remains were in the bloated stage of decomposition, as defined by Early and GofT(l986} during their studies in Hawaii. The head was characteris­tically blackened, while the torso appeared intact, although the abdomen was markedly inflated (Fig. 2). Ch.rysomya megacephala was collected from the remains as second instal' larvae, measuring 4 mm in length, and third instal' larvae, measuring 12~14 mm. Chrysolnya ru[i[acies was present on the head and neck areas of the remains as third instal' larvae. Those larvae collected from the head measured 12-14 mm, while those from the neck measured 7-9 mm. Larvae of a species of Phaenicia were also present on the remains as third instal' larvae measuring 5~6 mm. Rearing of these larvae to adults in the labora­tory was not successful and species identification was not possible. There are two species of Phaenicia associated with decomposing remains in Hawaii (Goff et al. 1986): P. cuprina (Wiedemann), and P. serricata Meigen. Of these, adults of only P. cuprina were collected from the outside of the blankets at the scene.

Representative samples of larvae and puparia of C. megacephala and C. rufi· facies were taken from the remains and blankets for rearing in the laboratory. These samples were held in environmental chambers at 26°C from 1600 on 31 December 1989 until adult emergence. The first adults of C. megaceph.ala emerged at 0100 on 2 January 1990, followed by nine adults at 0830, 3 January, and the remainder by 4 January. The first adult C. rufifacies emerged on the morning of 4 January 1990. Results of laboratory studies on the rates of devel~

opment of C. megacephaia (unpublished data) conducted in the Forensic Ento­mology Laboratory, University of Hawaii at Manoa, indicated a minimum requirement of 6,415 accumulated degree hours (ADH) for development from egg to adult at 23.5°C. Using data from rearing studies conducted at 26°C (unpublished data), it was determined that the period of development passed in

239 GOFF: Delayed Colonization of Remains

Fig. 1. Remains of a 32-yr-old female wrapped in two layers of blankets and tied with an elastic bandage.

240 J. Agric. Entomol. Vol. 9, No.4 U992}

Fig. 2. Remains of a 32-yr·old female after blankets had been unwrapped. Post­mortem interval estimate 13 d.

241 GOFF: Delayed Colonization of Remains

the environmental chamber at 26°C accounted for 858 ADH, leaving 5,557 ADH of development on the remains at the site. Climatic data were obtained from NOAA Weather Station 911, located at the Amorient Aquafarms, approximately 0.75 km from the discovery site. These data indicated that temperatures had ranged between 20.5 and 23.8°C during the time period in question. These tem­peratures were all well within the activity range for both C. mega.cephala and C. rufifacu,s. The rearing data for 23.5

0

C were used for calculations, as these most closely approximated the temperatures for the area during the time period. These calculations indicated a minimum period of 10.5 d postmortem interval.

As the remains had been wrapped in two layers of blankets and securely tied, access to the remains by flies for oviposition would probably have been delayed. In order to estimate the period of probable delay, the circumstances of the remains were recreated in a similar habitat in Kaneohe, also located on the windward side of the island of Oahu. All of the species of Oies potentially associated with the remains were also present at this site: C. megacephala, C. rufifacies, P. cuprina, and P. serricala. A freshly killed pig, 7 kg in weight, was wrapped in two layers of blankets and tied in the same manner as the remains. The pig was placed in a wire mesh (2.5 em sq mesh) exclosure cage in a semi-shaded location. Tempera­tures dw;ng this period were similar to those at the recovery site for the time period in question, ranging from 20.5 to 23.8°C. The pig was checked at 3-h inter­vals and flies excluded during the unwrapping and examination of the pig by nylon mesh netting. Under these conditions, flies first penetrated the wrappings, through folds around the head of the pig and o\,;posited 2.5 d following exposure. As the area was predominantly residential, it was not possible to replicate this experiment. Subsequent repetitions of the experiment have yielded times of2.4 to 3.0 d for penetration under similar temperatures at the same site in Kaneohe. For the present case, the time of 2.5 d was combined with the times indicated by the developmental stages recovered from the remains at the time of discovery to give a minimum postmortem interval estimate of 13 d.

Remarks

The estimate resulting from the above experiment and laboratory developmen­tal data fit well with facts independently obtained for this case. The victim had last been seen alive during the afternoon, L4 d prior to the discovery of the remains and had, later that day, been observed by neighbors "sitting or propped up" in the passenger seat of the defendant's truck. The defendant in this case, the victim's husband, was subsequently convicted of the charge of murder dUl'jng a trial held in HonoluJu.

The delay in colonization of the remains by insects at the death scene for the animal model, due to wrapping in the blankets serves to emphasize the necessity for consideration of all of the circumst.ances surrounding the remains when pro­viding a postmortem interval estimate. Other factors, as noted by Mann et al. (990), such as clothing or substrate, will also serve to alter the rate of insect colo· nization of remains and resulting patterns of decomposition. \\Then the forensic entomologist is dil'ectly involved in the p"oeessing of the crime scene, these factors will be noted. If the entomologist is not directly involved, suflicient data must be

242 J. Agric. Entomol. Vol. 9, No.4 (1992)

supplied to allow for consideration of these factors when providing the post­mortem interval estimate.

Acknowledgment

This is Journal Series No. 3532 of the Hawaii Institute of Tropical Agriculture and Human Resources.

References Cited

Baumgartner, D. 1.., and B. Greenberg. 1985. Distribution and medical ecology of blow nies (Diplera: Calliphoridae} of Peru. Ann. EntomoL Soc. Am. 78: 565-587.

Draaek, L. E. 0., and P. F. ReHer. 1986. Dispersal, density and habitat preference of the blow-nics Chrysom)'a. albiceps (WD) and Chrysomya, marginalis (WD) (DipLero: Cal­liphoridae). OndcrstepoorLJ. Vet. Res. 53: 13-18.

Early, M., and M. L. Goff. 1986. Arthropod succession patterns in exposed carrion on the island orO'ahu, Hawaiian Islands, USA. J. Med. Entomol. 23: 520-531.

Erzinclioglu, Z. 1985a. Immature stages of British Calliphora and CyllOmia. with a re­evaluation of the taxonomic characters of larval Calliphoridae (Dipt.eral. J. Nat. Hist. 19: 69-96.

1985b. Entomological investigation ofa concealed corpse. Med. Sci. Law 25: 228-230. Goff, M. L., and C. B. Odom. 1987. Forensic entomology in the Hawaiian Islands: three

case studies. Am. J. Forensic Merl. Pathol. 8: '15-50. Goff, M. L., M. Early, C. B. Odom, and K. Tullis. 1986.·A preliminary checklist of arthro­

pods associated with exposed carrion in the Hawaiian Islands. Proc. Hawaii. Entomol. Soc. 26: 53-57.

Goff, M. L., A I. Omori, and K. Gunatilnkc. 1988. Estimation of postmOitem interval by arthropod succession: three case studies ftom the Hawaiian Islands. Am. J. FOI'ensic Mod. Patho!. 9: 220-225.

Goodbrod, J. R., and M. L. Goff. 1990. Effects of lan'al population density on rates of development and interactions between two species of Chrysomya (Diptera: Calliphori­dae) in laboratory culture, J. Med. Entomol. 27: 338-343.

Greenberg, B. 1985. Forensic entomology: casc studies. Bull. Entomol. Soc. Am. 31: 25-28. Hawley, D. A, N. H. HaskeU, D. G. McShaffrey, R. E. Williams, and J. E. Pless. 1989.

Identification orred "fiber": chironomid larvae. J. Forensic Sci. 34: 617-621. Liu, D., and B. Greenberg. 1989. Immature stages of some nics of forensic importance.

Ann. Entomo!. Soc. Am. 82: 80-93. Lord, W. A, E. P. Catts, D. A Scarboro, and D. B. Hadfield. 1986. The green blow ny,

Lucillia iUuslris (lI,'Jeigen), as an indicator' of human post-mortem interval: a case of homicide ftom Fort Lewis, Washington. Bull. Soc. Vector Eco!. It: 271-275.

Mann, R. W., W. M. Bass, and L. Meadows. 1990. Time since death and decomposition of the human body: variables and observations in case and experimental field studies. J. Forensic Sci. 35: 103-111.

Nuorteva, P. 1977. Sarcosaprophagolls insects as forensic indicators, pp. 1072-1095. In Tedeschi, C. G. W. G. Eckert. and L. G. Tedeschi [eds.l, Forensic medicine, a study in trauma and environmental hazards, vol. 2. W. B. Saunders, Toronto. pp.787-1159.

243 GOFF: Delayed Colonization of Remains

Rodriguez, W. C., and W. M. Bass. 1985. Decomposition of buried bodies and methods that may aid in their location. J. Forensic Sci. 30: 836·852.

Tullis, K., and M. L. Goff. 1987. Arthropod succession in exposed carrion in a tropical rainforest on O'ahu, Hawai'i. J. Merl. Entomol. 24: 332-339.