Posted on 07/24/2002 10:44:59 PM PDT by FresnoDA
Bugs: The best witnesses? |
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On one side there are Danielle van Dam's fingerprints, her blood drops, strands of the 7-year-old's blond locks, hair from a dog like her weimaraner and carpet fibers that seem to be from her room. There is child pornography and a convoluted alibi even the defendant calls "weird." On the other side, the side for David Westerfield's acquittal, there are bugs. The pile of evidence painstakingly assembled by prosecutors in Westerfield's capital murder case got a jolt last week from an entomologist who suggested that insect evidence from the 7-year-old's body may exonerate the defendant, who is accused of abducting Danielle from her bedroom, killing her and then dumping her body.
Its practitioners say forensic entomology, which stretches back to 13th century China and has gradually gained acceptance in American courtrooms over the past two decades, is both art and science. There are only nine certified forensic entomologists in North America and about 30 more who offer their expertise in criminal cases without certification. When done correctly, a study of flies, maggots and beetles at a crime scene can yield crucial evidence about a victim's death, including the time and location, whether the victim had drugs in his system, and in some cases even the DNA of the perpetrator. But more than other forensic sciences like DNA analysis, forensic entomology eschews straightforward analysis. For analysis concerning time of death by far the most common task for entomologists in criminal cases there are no mathematical formulas, no easy calculations. Accuracy depends on the scientist's ability to determine how a host of variables at the crime scene, including temperature, precipitation, time of day, humidity and geography, affected insect life. "If you are not a very imaginative person as a scientist, you won't go far," said K.C. Kim, a Penn State professor and certified forensic entomologist. The subjectivity of the field makes for what another forensic entomologist, Jason Byrd of Virginia Commonwealth University, calls "showdowns" professional disputes over results. According to Byrd, haggling over conclusions has become increasingly common in the last three or four years as lawyers have become more familiar with the evidence and how to attack its credibility. "A court case with a single entomologist is a thing of the past," said Byrd, a certified entomologist who consults on about 100 criminal cases a year. A "showdown" seems likely in the Westerfield case. Just two days after damaging testimony from the defense entomologist, the San Diego district attorney's office hired M. Lee Goff, an entomologist from Chaminade University in Hawaii, to consult on the case.
The defense expert, David Faulkner, is particularly difficult to attack because he was initially hired by the prosecution. Faulkner, a research associate at the San Diego Natural History Museum, attended Danielle's autopsy and collected insects from her remains. Searchers found the second-grader in a trash-strewn lot three and a half weeks after she vanished. Her body was badly decomposed and the medical examiner could only offer prosecutors a wide range 10 days to six weeks for her time of death. Investigators hoped Faulkner could narrow that window to Feb. 2, 3 or 4, the days immediately following Danielle's abduction when Westerfield's activities seemed suspect. Faulkner examined maggots from her body and told authorities the insects began growing 10 to 12 days prior, putting the first infestation between Feb. 16 and Feb. 18. Infestation can start as soon as 20 minutes after a dead body is dumped outdoors. Faulkner's conclusion did not fit prosecutors' theory. Westerfield was under constant police surveillance from Feb. 5 until his arrest, offering him no opportunity to dump her body in the window of time the entomologist's testimony indicated. Faulkner quickly became a witness for the defense. The lives of insects If prosecutors get Goff or another expert to rebut Faulkner's findings, he or she will likely attack the defense expert on how he calculated the post-mortem interval (PMI), entomologist-speak for the first infestation. Insect life arrives at a dead body in stages. Immediately, flies land on a body. In as little as 20 minutes, they lay eggs. Those eggs hatch into maggots in a day, and those maggots feed on the body. The maggots molt repeatedly, and each stage of larvae is slightly larger, indicating to entomologists how long the insects have lived in the body. Beetles also are attracted to decaying flesh, and the size of their larvae also indicate the time they have been at the body. But just recognizing the size of the larvae is not enough. Entomologists must also determine the growth rate of the insects. There are two ways to do this. Experts can simply match the size to textbook tables showing the rapidity of growth in a climate-controlled laboratory or they can try to determine the growth rate by themselves. The latter is considered the most accurate, but also the most difficult. "It has a lot to do with the investigator's experience and intelligence and that has a lot more to do with art than science," said Kim of calculating the PMI. Among the crucial factors is weather. Hot temperatures mean quick growth, cold temperatures mean slow or no growth. Wind affects the rate as does access to water and other forms of food, like trash cans. Rain and humidity play a role, as well as exposure to sunlight. In the Westerfield case, prosecutor Jeff Dusek grilled Faulkner about how February's hot, dry weather might have affected his PMI conclusion. Faulkner acknowledged there were fewer flies last winter in San Diego than ever before, but refused to budge off his estimate. Entomologists also consider unnatural factors, like whether a blanket or sheet around the victim may have retarded insect life. Goff once worked on a case in Hawaii involving a woman missing 13 days. She was discovered murdered and wrapped in blankets. The life stages of the insects indicated a PMI 10 and a half days prior. To determine how the blankets affected the PMI, Goff wrapped a pig carcass in blankets and left it in his backyard. He found it took two and a half days for the flies to penetrate the blanket. Dusek quizzed Faulkner about the impact of some sort of shroud in the Westerfield case. There is no evidence Danielle's body was wrapped in a blanket, but the prosecutor got Faulkner to admit that a covering, perhaps later dragged away by animals, might have skewed his results. Will the jury care? But even when there are disagreements between entomologists on results, they rarely involve as wide a gap as in the Westerfield case. "A lot of the disagreements involve a variation in one day, two days," said Richard Merritt, a certified forensic entomologist and professor at Michigan State University. "Not over a week and a half. If it's that big a time, someone screwed up." If the prosecution cannot find an expert who substantially disagrees with Faulkner, the bug evidence would appear to be the defense's chief argument to jurors at closings. The defense has tried to chip away at the other forensic evidence. Defense lawyer Steven Feldman has suggested Danielle secretly played in Westerfield's motor home and left hair, blood and fingerprints on that occasion. Evidence in his home, the lawyer has hinted, might have been deposited when the girl and her mother sold him Girl Scout cookies. And fiber evidence could have been transferred when Danielle's mother was dancing with Westerfield the night of the abduction. None of those explanations carry the certainty of Faulker's testimony. But just how persuasive Faulkner's testimony will ultimately be is a subject of hot debate in San Diego, where the case dominates the media. Former prosecutor Colin Murray said the mountain of other physical evidence pointing toward Westerfield's guilt made the insect evidence little more than a footnote. "You're asking a lot of this jury to acquit this guy on capital charges based on the presence of bugs," he said. Even without a rebutting witness, Murray said, prosecutor Dusek could undermine the entomological evidence in closings by harping on the subjectivity of the field and asking the panel to instead rely on common sense. "Common sense tells you, if you're just looking at her body, that it's been out there a long time. It's severely decomposed," said Murray. But Curt Owen, a retired public defender, disagreed, saying that depending on how the prosecution rebuts the evidence, the case could end in a hung jury or even acquittal. "It may not be enough to say he's innocent," Owen said, "but it certainly is enough to introduce reasonable doubt." |
You mean that it could be cold or hot as long as there is no moisture available?
I can't type and catch it all at the same time so I missed some of it.
As law enforcement realized the value of this information, increasingly more entomologists got involved. M. Lee Goff, professor of entomology at the University of Hawaii at Manoa and author of A Fly for the Prosecution, is a consultant to the Honolulu medical examiner. His book spells out the many contributions that an entomologist can make in a death investigation.
"Most frequently the forensic entomologist is asked to estimate the postmortem interval based on insect activity," Goff points out. "This is actually an estimate of the period of insect activity, not the actual postmortem interval. The two are often quite close, as the insects arrive and begin their activity shortly following death. In some instances, there may be factors that serve to delay the onset of insect activity, and these must be considered."
Other contributions include:
Goff's first experience at a crime scene was in 1984 with the discovery of the body of a female in Hawaii's Hau Tree Park area, located in Ewa Beach. "I had previously participated in a number of cases at the morgue, but this was the first time someone got me out of bed to go to a scene." Since then, he's been increasingly more involved.
In the case of one victim who appeared to have been dead for at least two weeks, the insects had done quite a job. Goff and his assistant collected the specimens and took them back to his lab. They found three species of maggots in different stages of development, which they measured and preserved. They also put some into a rearing chamber to complete their development into adultsthereby differentiating them more definitively. Collecting evidence of one more fly species and two types of beetle, Goff put all of this information into a computer to see if a program that he'd developed would provide a PMI.
The analysis disappointed him: Either no such body existed or there were two different bodies. "In trying to analyze what had gone wrong," he says, "I had to reevaluate the data I had provided to the computer. That led to the discovery of the role that the positioning of the body played in altering the insect activity---particularly the Sarcophagidae larvae." In other words, while it is generally the case that two species would not be on a corpse in the specific stages in which they were found on this one, there was something unique about the crime scene. Goff returned and saw that the victim had been partially submerged, which meant that the flies that might otherwise have left as tissues lost moisture had remained. That was a lesson about the limitations of databases: Any given case may have distinct characteristics that throw the data off.
As time passes, different groups of insects come and go in the process of assisting corpse decomposition. As each feeds on the body, it changes the body for the next group, which is attracted to those particular changes.
Entomologists agree that there are four main types of direct relationships:
"The relationships of the insects to the body, in terms of how they make a living," Goff explains, "are determined by the biology of the insect. Parasites remain parasites, although in some cases the tissue-eaters have been known to switch to predation as the body is consumed. Yet habitat and climatic factors can alter their periods of activity on the body. If the particular insect feeds on dried tissues, it may appear earlier in a hot, arid habitat and possibly not appear at all in a moist habitat. These changes may affect the pattern of succession, but the roles of the individual insects are set by their evolution."
The job of the forensic entomologist is to interpret these various relationships in order to offer information to law enforcement officers that will assist in leads. "At present," says Goff, "entomology is relatively well accepted by crime scene investigators. When I first began, we were regarded as having limited value. Over the years, with educational outreach and careful work, we have become a recognized discipline."
For research---since there's only one Body Farm at this time---he relies on pigs. "I have selected sites for my studies based on the records of localities in which bodies have been encountered. For each study, I use three pigs. One is placed directly on the ground, or on whatever substrate I'm investigating. This pig is left undisturbed for the duration of the study. A second pig is placed onto a welded wire mesh weight platform. This pig is used to determine the rate of biomass removal by weight and will be weighed each time the site is visited. It's also equipped with thermocouple probes inserted into the mouth, abdomen and anus to determine changes in internal temperatures related to decomposition. The third pig is also put on a welded wire mesh platform placed directly on the substrate. This pig serves for sampling of insects and other arthropods. Equipment for recording climatic data is placed at each site, including rain gauge and hygrothermograph."
They then record all factors and add their results into an expanding database.
What Goff finds satisfying about this work is its immediate and practical application. "In many of my academic research projects, I never see any application of the results. Here I see an actual situation and a resolution. I must admit to a certain level of excitement in participating---I'm only human---but I never allow this to interfere with my objectivity."
In 1984, he and several other forensic entomologists began meeting informally, and eventually they decided to form a certifying board. "We modeled ourselves after similar boards in anthropology, odontology and pathology. It was finally incorporated in the State of Nevada in 1996 as the American Board of Forensic Entomology."
In the future, Goff believes that advances in technology will make a significant contribution to the discipline. "For example," he says, "the use of DNA technology to identify immature specimens and extract material from gut contents to allow for individualization of both suspects and victims. Also, we need to focus on standardizing techniques for determining basic life cycles. At present, the data are quite varied, leaving gaps when cases come to trial. Yet even within the relatively new area of drug detection, there have been improvements that allow for more precise analyses. I think it's going to get even more exciting in the relatively near future."
Forensic anthropologists appear to have a considerable range of skills for assisting in death investigations. From art to bugs to bones, they make their mark.
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He's not a bugologist...but is an anthropologist...on bugs/incests...early literature says that insects plays a major roles with bodies. He studies insects their pattern of activity, how they mature and interact with that body... various types of bugs will be excluded because of the mummification. larvaes can't penetrate hardened skin
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