A Fly for the Prosecution: How Insect Evidence Helps Solve Crimes

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Chapter One

BEGINNINGS

Anyone involved in death investigations quickly becomes aware of the connection between dead bodies and maggots. Insects are major players in nature's recycling effort, and in nature a corpse is simply organic matter to be recycled. Left to its own devices, nature quickly populates a corpse with a diverse community of organisms, all dedicated to reducing the body to its basic components. Very quickly, "worms" appear, crawling out of the various orifices. Until quite recently, most death investigators regarded these insects as merely a sign of decay, to be washed away or otherwise disposed of as quickly as possible, rather than potentially significant evidence. Thus while other forensic sciences, such as toxicology, forensic pathology, blood-spatter analysis, and ballistics, developed into accepted forensic tools, beginning in the late 1800s, forensic entomology was seldom practiced.

    Yet the application of insect evidence to criminal investigations is not a new idea. A form of forensic entomology was practiced at least as early as the thirteenth century. In 1235 a Chinese "death investigator" named Sung Ts'u wrote a book entitled The Washing Away of Wrongs , which was translated into English by B. E. McKnight in 1981. Sung tells of a murder in a Chinese village in which the victim was repeatedly slashed. The local magistrate thought the wounds might have been inflicted by a sickle. Repeated questioning of witnesses and other avenues of investigation proved fruitless. Finally, the magistrate ordered all the village men to assemble, each with his own sickle. In the hot summer sun, flies were attracted to one sickle, because of the residue of blood and small tissue fragments still clinging to the blade and handle. Confronted with this evidence, the owner of the sickle confessed to the crime. The magistrate's action demonstrates considerable knowledge of the activity patterns of the flies, which were certainly blow flies. Indeed, in other parts of the book, Sung talks about the blow flies' activities in natural body openings and wounds, including an explanation of the relationship between maggots and adult flies, and discusses the timing of their invasion of a corpse.

    Not until several centuries later, in 1668, was the link between fly eggs and maggots discovered in the West. Before then, people did not realize that maggots hatched from the eggs flies laid on exposed meat or decomposing bodies. Francesco Redi's studies of meat that was exposed to flies and meat that was protected from flies resulted in a major discovery. His observations of fly infestations on the exposed meat demonstrated the link between the flies' egg laying and the maggots, and disproved the concept of spontaneous generation. Before Redi, maggots were believed to arise spontaneously from rotten meat, not emerge from fly eggs. If my telephone log at the University of Hawaii at Manoa is any indication, quite a few people still think that maggots are worms with no connection to flies; one man even told me that maggots normally live "inside people" and only come out after we die.

    Unfortunately, Redi's discovery did not lead immediately to the use of entomological evidence in death investigations. The first record of the use of insects in a forensic investigation in the West dates from 1855. During a remodeling of a house outside Paris, the mummified body of an infant was discovered behind a mantelpiece. Suspicion soon centered on the young couple then occupying the house. An autopsy was performed on the infant by Dr. Bergeret d'Arbois of nearby Jura, Switzerland, who concluded that the child had died in 1848. He noted evidence that a flesh fly, Sarcophaga canaria, had exploited the body during the first year (1848) and that mites had laid their eggs on the dried corpse the following year (1849). Bergeret's analysis of the insect evidence demonstrated to the satisfaction of the police that the death had occurred much earlier than 1855 and that the logical suspects were the occupants of the house in 1848, and they were subsequently arrested and convicted of the murder. The methods employed by Bergeret d'Arbois in his analysis are essentially the same as those forensic entomologists use today in estimating the time since death. He recognized and drew conclusions from the predictable pattern of succession of different insect species onto a corpse, and saw the significance of the duration of the life cycles of different carrion-frequenting insects. But although the assumptions underlying his analysis were correct, he appears to have misinterpreted some of the life cycles of the insects involved, and his conclusions would probably not have passed muster in a modern courtroom.

* * *

FORENSIC ENTOMOLOGY SHOULD logically have continued to develop steadily, with new discoveries arising from the findings of previous research. But progress was uneven and sporadic. Research was usually conducted in response to a murder and often ceased once the case was solved. There were some exceptions, particularly the work of J. P. Megnin in France. During the late 1800s, he published a series of papers on medicocriminal entomology that alerted both doctors and lawyers to the usefulness of entomological evidence. Possibly the most significant of these papers was La faune des cadavres: Application l'entomologie a la medicine legale , which was published in 1894. The central thrust of Megnin's work was that the postmortem interval can be determined by analyzing the various species of arthropods--invertebrates with a segmented body and paired, jointed legs, such as the insects, the mites, and the spiders--that are present on a decomposing body, without regard to their age. Today's forensic entomologists recognize this principle, but usually also take into account the age of each species in determining the postmortem interval.

    In the mid-1930s entomological evidence came to the fore in a particularly brutal murder case, recently chronicled in New Scientist by Zak Erzinçlioglu. On September 29, 1935, a woman spotted a severed human arm while looking over a bridge spanning a small stream in Scotland. Ultimately, over 70 pieces of two badly decomposed corpses were recovered from the area, since known as the Devil's Beef Tub. The reassembled parts were eventually identified as the remains of Isabella Ruxton, the wife of a local physician named Buck Ruxton, and her personal maid, Mary Rogerson. Mrs. Ruxton had last been seen alive on September 14. Among the varied pieces of evidence collected at the scene was a group of maggots feeding on the decomposing body parts. These maggots were sent to a laboratory at the University of Edinburgh, where A. G. Mearns identified them as maggots of a blow fly, Calliphora vicina, and estimated that they were between 12 and 14 days old when they were collected. Since these maggots had developed from eggs laid on the body parts by adult flies in the vicinity, the bodies could not have lain near the stream for less than 12 to 14 days. This was the minimum time between the deaths and the discovery of the dismembered bodies. Suspicion fell on Buck Ruxton for a number of reasons, and the entomological estimate of the time of death became highly significant. The two bodies had been dismembered so skillfully that authorities believed the perpetrator had some knowledge of the human anatomy. Dr. Ruxton had been seen with a cut finger on September 16. In addition, one of the severed heads was wrapped in clothing belonging to one of the Ruxton's children, and the cleaning woman reported blood stains and foul odors in the Ruxton residence on September 17. All the evidence pointed toward Ruxton as the murderer, and the insects had been instrumental in pinpointing the time of death. Although he never confessed, Buck Ruxton was convicted of both murders and hanged.

    More recently, Pekka Nuorteva of Finland has made important contributions to forensic entomology. The majority of his cases were murders, but one case he related in 1977 dealt with a dispute over the cleaning of government offices. During the summer, an official in the Finnish government noticed a lot of large maggots under the carpet near his office door. The official called for the cleaning woman and asked how often she cleaned the carpet. She replied that the carpets were cleaned daily and that she had last cleaned his office the evening before. The official could not believe that maggots over 1 centimeter long had developed overnight, and the cleaning woman was dismissed for lying and not properly performing her duties. As a matter of curiosity, a veterinarian was asked to look at the maggots and the carpet. He did not believe that the maggots could have developed by feeding on the synthetic fibers of the carpet, so he collected some of the larvae and sent them to Nuorteva for his opinion. The larvae were post-feeding maggots of a species of blow fly, Phaenicia sericata . At this stage of its development, a blowfly maggot stops feeding and migrates away from the food source to pupate. Nuorteva concluded that these larvae had probably developed on the carcasses of mice in the building or on some improperly stored food materials, definitely not on a synthetic carpet. During the night, they had migrated away from their food source and onto the carpet. Given this information, the official rehired the cleaning woman, but there is no record of any apology.

* * *

IN THE UNITED STATES, Bernard Greenberg of the University of Illinois at Chicago is widely regarded as the father of forensic entomology. His original training was in acarology, the study of mites, at the University of Kansas. But after obtaining his master's degree, Greenberg shifted his attention to the blow flies that constitute the family Calliphoridae and he is now a world authority on this family. Over the years he has been an innovative researcher and mentor to a number of graduate students. His research on the biology and life cycles of the many species of blow flies provided a strong basis for forensic work, and for many years he was essentially the only entomologist in the United States who devoted a major part of his research effort to issues important in forensic entomology.

    During the mid-1960s, a graduate student in North Carolina named Jerry Payne began to lay the groundwork for another modern approach: succession. Simply stated, succession is the idea that as each organism or group of organisms feeds on a body, it changes the body. This change in turn makes the body attractive to another group of organisms, which changes the body for the next group, and so on until the body has been reduced to a skeleton. This is a predictable process, with different groups of organisms occupying the decomposing body at different times. In his landmark paper, published in the journal Ecology in 1965, Jerry Payne detailed the changes that occurred during the decomposition of pig carcasses that were exposed to insects, compared to the changes in pig carcasses that were protected from insect activity. This work built on and refined studies conducted almost 70 years earlier in France by Megnin. Megnin recognized nine stages of decomposition, but Payne recognized only six, introducing the system currently used by most forensic entomologists. Payne further emphasized the great variety of organisms involved in the process, recording over 500 species. Payne also conducted other experiments, including studies of submerged carrion.

    Although others had studied decomposition before Payne, his work has received the greatest attention, possibly because of the thoroughness of his research, but also in part because of the status and circulation of the journal Ecology . Other excellent studies of decomposition--such as work by H. B. Reed, Jr., on insects involved in the decomposition of dog carcasses and G. F. Bornemissza's work on the effects of guinea pig decomposition on soil-dwelling arthropods--have appeared in regional journals and not received the widespread attention they deserved.

    A number of other excellent biological and succession studies were published from the 1950s on, but none of these was undertaken with its forensic potential in mind. These studies, frequently conducted by graduate students, usually focused on agricultural or public health problems: In the 1950s and 1960s, there was much concern about the possible aftermath of an atomic attack in a society with few provisions for dealing with the public health problems presented by the accumulation of millions of dead bodies.

    While entomologists were largely ignoring forensics in their publications, physical anthropologists were concentrating on the changes that occur in a human body between death and skeletonization. They recognized the major roles played by insects in the decomposition processes. Initially, the subject was discussed only in notes and in observations of isolated cases involving insects. But with the establishment in 1981 of William Bass's Anthropological Research Facility at the University of Tennessee, controlled studies of human remains began to be conducted. Work by William Rodriguez and Bill Bass during the 1980s yielded significant new information about the colonization of exposed and buried bodies by insects.

* * *

IT WAS IN the early 1980s that I became involved in forensic entomology. Before then, I had been conducting research in acarology. I had completed my Ph.D. in entomology at the University of Hawaii at Manoa in 1977, and moved immediately from the university to the privately endowed Bernice Pauahi Bishop Museum some 7 miles across town. There I became the principal investigator for a study of the classification of the chiggers of Papua New Guinea funded by a grant from the National Institutes of Health. I was dismayed to discover that the NIH grant paid less than I had earned as a graduate student. To supplement my income, I took on a series of side jobs, ranging from occasional entomological consultations to providing security for wholesale gift and jewelry shows.

    One of the benefits of the NIH grant was a stipend to attend the annual meetings of the Entomological Society of America. In December 1981 the meeting was held in San Diego at the Town and Country Hotel. Since I was on a limited budget, I stayed at another hotel eight freeway lanes and three fences away from the main meeting hotel. This meant either I had to walk 2 miles to get to the meetings without crossing the freeway through traffic or I had to dodge eight lanes of speeding cars to get to the other side. I walked the 2 miles. As a result, I went to the meetings early in the morning and did not return to my hotel until late in the evening, an arrangement that led to my attendance at several presentations I normally would have missed. Among these was an early-morning presentation by Lamar Meek of Louisiana State University.

    Meek talked about the research he was conducting on decomposition, ending with a discussion of a murder investigation. He illustrated the first part of his talk with slides of decomposing pigs, then shifted to slides of human remains. As the slide show went on, I began to think that this field might hold some promise for me. I already had my Ph.D. in entomology, and I had had first-hand experience with dead bodies during my stint in the U.S. Army. I had been drafted a couple of months after earning my bachelor's degree in zoology, and I spent most of my 2 years in the military in the morgue at the U.S. Army Hospital at Fort Ord, California, but also had a couple of tours of duty with a chemical, biological, and radiological warfare unit at Edgewood Arsenal in Maryland. There I was a subject in tests of riot-control gasses, not the most enjoyable period of my life. This combination of activities left me with a better working knowledge of human anatomy than I had acquired in formal classes. By 1981, in short, I had some knowledge of insects and was fairly confident of my ability to deal with dead bodies. More important, forensic entomology appeared to be a more interesting line of work than giving farmers advice on how to keep spider mites from damaging tomato plants.

    On my return to Honolulu from San Diego, I began to look for background material and names of other people working in the field. There was not much in the entomological literature specifically devoted to forensic entomology. I found most of the older references and a few more recent papers, but it quickly became apparent that if I really wanted to pursue this field, I would have to involve myself with people I had not dealt with on a cooperative basis before. Since my only prior experience with the police was being on the receiving end of traffic citations, I decided to start with the medical examiner.

    The medical examiner in Honolulu at the time was Charles Odom. He had a particularly diligent secretary screening his calls, and for a couple of months whenever I called Odom was out of town. Eventually, I did manage to get in touch with him and persuade him to meet with me. We had lunch together at the Willows Restaurant near the University of Hawaii at Manoa. By the end of the meal we had decided that if we could discuss maggots and decomposing bodies while eating curry over rice, we could probably work together.

    I soon discovered that agreeing to work together and actually beginning to work together are not the same. For one thing, despite the impression conveyed by such late-night television staples as Hawaii Five-O and Magnum, P.I. , the homicide rate in Hawaii is extremely low compared to that in the other 49 states. And on Oahu, where I do most of my forensic work, the bodies of murder victims are usually discovered very quickly because the island is relatively small and because the terrain and the hot and humid climate do not favor lengthy concealment of corpses. For these reasons relatively few death investigations in the city and county of Honolulu involve bodies that have been decomposing for more than a brief period of time. Consequently, at least at the beginning, I became involved in murder cases only if I contacted the medical examiner's office whenever I heard or read in the newspapers about a death involving a badly decomposed body.

    Apart from this obstacle, I met surprising resistance from the Bishop Museum. The feeling was that I might involve the museum in situations that would generate unfavorable publicity and perhaps even lawsuits resulting from my testimony. I found both concerns hard to understand, particularly the bad publicity: it's difficult to see how helping solve a murder can be considered "bad." While I was attempting to overcome this resistance, a solution arose in the form of an opening in the Department of Entomology at the University of Hawaii at Manoa.

    The College of Tropical Agriculture and Human Resources seemed to be the perfect place for forensic study. The position required me to teach courses in acarology and classes in medical and veterinary entomology (about insects and other arthropods as the causes or vectors of human and animal diseases), and help ensure the well-being of agriculture in the state of Hawaii. I was well qualified for the teaching requirements, but the university's definition of agriculture at that time seemed restricted to the activities of farmers growing plants for food. So I redefined both "agriculture" and "human resources" in my own mind and accepted the position. There were several advantages to my new position, not the least of which was a sense of financial and professional stability--grant funds, and with them the job, have a way of expiring on very short notice. Moreover, the university provided me with a base of operations that was more acceptable both to the police and to the medical examiner than a privately funded museum. An unforeseen bonus was the potential for graduate students to assist in research projects. At any university and in any department there are always some students willing to explore new and unusual areas. Over the years, I've managed to attract more than my share of these students to my projects and their work has always been productive.

    At about the same time, several other entomologists and parasitologists began to explore forensic entomology. Some, such as Paul Catts, had been consulted previously on criminal cases. Others, such as Wayne Lord, had spent more time investigating the ecological aspects of decomposition. I myself was still exploring the field. Of the group, only Bernard Greenberg was involved in forensic entomology on any kind of continuing basis.

    Over the next couple of years, we began to gravitate toward each other during the annual meetings of the Entomological Society of America, assembling for the first time in 1984 at the annual meeting in San Antonio. Lamar Meek had organized a symposium on forensic entomology, and after the morning session we decided to lunch together. This was the beginning of a tradition. Initially, we got together for lunch, but we soon shifted to breakfast meetings. Sitting around the table, we created an informal group called CAFE. Theoretically, this stood for Council of American Forensic Entomologists, but in practice it meant that we met in various cafés. The group had no official organization although Paul Catts usually made any reservations for tables. The only real criteria for membership were being able to get up for breakfast and being able to look at pictures of decomposing bodies while eating. Early on, Paul Catts began to refer to the group as the Dirty Dozen and the name stuck.

    This group has grown over the years and now numbers about 15 people in the United States and Canada who are routinely involved in forensic entomology. This informal association has provided a forum for the exchange of ideas and moral support in our studies. Many of the techniques I talk about later in the book were developed as a result of the interactions between members of this group. After 12 years, in 1996, we finally formed an official organization, the American Board of Forensic Entomology.

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