'Welcome to CSI–Bethesda'
Science Plays Widening Role in Forensic Analysis
By Rich McManus
Photos by Ernie Branson
On the Front Page...
It's getting so that the world's bad guys had better earn their Ph.D.s before they commit their crimes; a STEP Science for All session on "Forensic Science: Unraveling the Riddles" showed not only that it's harder to get away with bad deeds than ever before (the leadoff speaker showed you can glean information simply from patterns of spattered blood), but also that damning evidence persists long after the misdeed, from minutes (Virginia's chief medical examiner offered graphic evidence of postmortem rigor and livor) to months (a scientist whose company specializes in DNA identification reported on post-9/11 recovery efforts) to decades (an Army scientist is teasing out the mysteries of why the 1918 influenza pandemic was so virulent) to centuries (an authority on exhumations detailed how a skeleton may speak).
Continued...
Small wonder, then, that the Dec. 13 session drew an overflow crowd to Lister Hill Auditorium. "Welcome to CSI–Bethesda," quipped Teresa Nesbitt of the Center for Scientific Review, who chaired the event's organizing committee. "Today we're going to find out that dead men really do tell tales."
Leadoff speaker Ross Gardner, police chief in Lake City, Ga., a suburb of Atlanta, gave a sort of Crime Scene 101 primer, arguing that such scenes are really laboratories dotted with physical evidence that tells a story. An objective, rational approach to deciphering evidence ideally leads to justice for all parties involved, he said. "It's like assembling a jigsaw puzzle, with a nasty twist," he explained. "We have the archaeologist's dilemma — how to make sense of artifacts." Despite relying on the tools and spirit of science, Gardner says crime scene investigation remains an art. Much depends on how physical evidence gets interpreted. "Physical evidence will never lie to you," he said, "but we can misinterpret it." Gardner said a major fault of his profession is a tendency to let conclusions determine the facts, rather than vice versa. |
Quoting one of the founding fathers of crime scene investigation, Gardner said, "Every contact leaves its trace." Those traces are becoming more susceptible to scientific study, he showed. Police can use a SceneScope employing ultraviolet and other sources of light to make body fluids and fibers more visible; they use "superglue fuming" to stabilize latent fingerprints; SPR, or small particle reagent, allows detectives to raise prints from wet surfaces; and DNA identification is getting more powerful every year — the latest advance is STRs, or short tandem repeats, a technology that combines restriction fragment length polymorphisms with PCR amplification.
Interestingly, Gardner thinks DNA evidence is oversold: "DNA doesn't in and of itself define guilt," he cautioned. And though he said that detectives' ability to recover fingerprints is getting better, analysis of the prints remains a relatively static field.
Concluding his talk, he demonstrated that study of shards of broken glass can reveal which direction the force came from, and that soil science has become so accurate that a talented investigator can tell you exactly where in your backyard a particular specimen originated.
Demonstrating that "the body itself is a crime scene," was Dr. Marcella Fierro of Virginia Commonwealth University, who is the state's chief medical examiner. A forensic pathologist, she explained the many instances of death that call for investigation by a medical examiner. As firm an adherent of the scientific method as Gardner, she proffered "Tylk's Law: Assumption is the mother of all foul-ups." Witness to the aftermath of all kinds of grisly crimes, Fierro shared the results of her studies with professorial, sometimes mordantly humorous, detachment. For example, she observed that "only on TV do they determine time of death with such accuracy," pointing out that many variables, including body temperature, livor (the pooling of blood, due to gravity, in certain parts of the body) and rigor (stiffness following death) must be taken into account. "Time of death is always an estimate," she said, "and is based on the window of time within which the victim was last reliably seen alive and when he or she was reliably found." |
Because a decaying body is subject to a predictable pattern of colonization by maggots and carrion beetles, entomology has had more to offer forensic medicine recently, she said. The contents of a victim's stomach can also be valuable, Fierro noted, as is study of other major organs. The heart, for example, always gets a look at autopsy because coronary artery disease is the leading cause of sudden, unexpected, natural death, she said. Other common killers are arrhythmias, fatty livers, asthma and diabetic ketoacidosis. Cocaine abuse is particularly dangerous for the heart, she warned.
Victims of car crashes, she said, suffer a typical constellation of injuries. "There is a classic pattern for the unbelted driver," she explained. Other dead giveaways include "the unmistakable" arborization pattern in the skin of lightning-strike victims and stress ulcers erupting in the stomachs of victims who died physiologically stressed over a number of hours.
Fierro occasionally interrupted her remarks with editorial asides, including a call for more federal money devoted to forensic pathology research, and pleas for mandatory helmet-wearing for motorcyclists and mandatory hard-wired smoke detectors for residences. She also predicted new dilemmas as terrorism becomes a more prominent form of homicide: sometimes victims' bodies are too toxic to return to the family following autopsy. "This culture doesn't ascribe to mass graves," she observed. "Families want the remains of their loved ones back."
Sorting through evidence recovered from a mass gravesite was the dire task of responders to the World Trade Center on 9/11, including scientists from the Bode Technology Group, Inc., whose vice president and laboratory director Dr. Mitchell Holland offered examples of DNA's power as a "unique biometric tool." He suggested that all Americans might one day submit to DNA profiling, much as they now register for Social Security numbers and obtain driver's licenses. Such profiling would not only help catch more criminals, he argued, but would also offer a means of identification in the event of tragedy, establish paternity in disputed cases and help the nation keep track of immigrants.
He applauded the establishment of convicted offender databanks — DNA repositories (the largest of which is called CODIS, now holding more than 1.25 million samples) — that could help solve cases that lack suspects. He said the profiling is limited to "nonsense" DNA stretches that don't code for genes or traits. He assured "a profile is useless unless there's something to compare it to," or an "exemplar" sample. The typical profile he proposes would consist of 26 or more
numbers, corresponding with 13 or more regions |
The state of Virginia is "one of the most progressive users of DNA profiling in the U.S.," Holland reported, maintaining samples from more than 200,000 convicted offenders. He said the databank has resulted in more than 1,000 "cold hits" (solved cases) in Virginia so far; nationally, databanks have solved more than 6,000 cases.
"It's an extremely effective technology," Holland said, "but we're in our infancy in terms of our ability to use it." To enhance the field, he proposed two steps: build up DNA databases and establish labs willing to test cases that lack suspects.
"There are thousands of crime scene profiles without suspects in Virginia," he said, "and more than 45,000 in the U.S."
In Baltimore, there are more than 2,600 unanalyzed — for want of funds — rape kits, he reported, "and that's just the tip of the iceberg; there are probably 500,000 unprocessed rape kits nationwide." More and more perpetrators will be caught, and there will be far less crime" if his proposals come to fruition, he said. "The hits are starting to come more rapidly."
Holland, who said his company wants to hire 20 new scientists, said that 9/11 and various airliner crashes have made DNA identification a burgeoning field. Bode Technology received 2,000 partial remains, some only an inch long, within a month of 9/11, and in total analyzed some 13,000 WTC bone fragments, 5,500 soft tissue samples, as well as 3,200 reference samples from victims' families. "Our biggest challenge was a lack of references," he said, calling for voluntary nationwide sampling.
Damage from fire and water at Ground Zero reduced Bode's success rate in recovering useable DNA samples from a normal post-tragedy rate of 90-95 percent, to about 70 percent, Holland said. "Even fragments that came to us as literal charcoal got sampled," he said. "Everything that was recovered got tested."
He said methods of extracting and amplifying stretches of DNA are improving constantly, almost to the level of single-cell analysis (although he noted that there are anomalies at that level). At the very least, he recommended that those who pursue at-risk activities such as fire fighting, law enforcement, military service and work conducted in dangerous places (embassies, countries abroad) have their DNA profiled prior to deployment.
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"Exhumation should be the exception, not the rule," he assured the audience. But curiosity is nonetheless a strong goad; Starrs says his motto is, "You never know what's there until you're there."
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Playing multi-decade connect-the-dots with RNA fragments, Taubenberger and colleagues are trying to imagine scenarios wherein influenza A, a relatively fragile single-stranded RNA virus, can go from being fairly benign (the vast majority of flu patients recover, he said, though flu kills some 20,000 people in the U.S. annually, mostly neonates and the elderly) to being a widespread killer, even of young, healthy people in their prime. Eight AFIP specimens recovered from more than 100 autopsies conducted on soldiers killed by the 1918 pandemic yielded RNA viral fragments, Taubenberger said. "But they're in terrible shape and in tiny amounts." His team is trying to reconstruct the virus's entire genome from these tissues.
One of the bodies exhumed in Alaska had enough viral RNA to allow reconstruction of the entire genome. Taubenberger's team is also searching for influenza RNA in waterfowl, who along with pigs and people, were stricken by the 1918 flu. Six of 25 birds preserved from the era yielded flu virus RNA; AFIP scientists are sequencing chunks of the virus and have so far completed five of eight gene segments. But the question of the deadly strain's origins, and the key to its lethality, remains unanswered.
The AFIP team's studies are not merely academic. History shows that major flu epidemics occur every 30 years or so. The last one was in 1968, "so statistically speaking, we may be due for another pandemic. But we don't know when, how or by what strain," Taubenberger cautioned. "The outbreak of flu in chickens in Hong Kong in 1997 might be a warning sign," he said. "And flu spreads by jumbo jet now, not by steamship (as in 1918, when U.S. troops carried the virus to Europe)...I think it's clear that influenza epidemics are nothing to sneeze at."
To view the STEP session on forensic science in its entirety, visit videocast.nih.gov.
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