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But drives it where? There are plenty of experts who wonder if turning criminal science into a craze is a good thing. Solving crimes is not nearly so quick and reliable a job as a 46-min. story line would make it seem. Investigations can take months, evidence can get muddled and courts, dubious about all the new gadgetry, are often reluctant to trust it. And that doesn't touch the swamp of constitutional questions raised when a prosecutor tries to wade into a suspect's brain and DNA. "TV has romanticized forensic science," says Susan Narveson, head of the forensics lab of the Phoenix, Ariz., police department and president of the American Society of Crime Lab Directors. All this creates unrealistic expectations in the minds of the public and juries.
Part of the problem is that forensics has always been equal parts art and science, a point made in January when a Philadelphia judge threw out fingerprint evidence in a murder case after an expert could not explain to his satisfaction why such identifications are considered reliable. The judge later reversed himself, but, says assistant federal defender Robert Epstein, who brought a challenge to the admission of fingerprint evidence in a robbery case, "even if the judges are going to let [fingerprint evidence] in, it doesn't mean juries are going to accept it uncritically anymore."
At its best, then, forensics is an uncertain business, the onion-peeling exercise of investigating a crime using everything from shoe-leather detective work to the forensic accounting applied to Enron-type cases. Crimes of passion or violence, however, require a whole different set of tools, and it's here that much of the new science is found.
Ever since the evidentiary orgy of the O.J. Simpson trial, forensics for many people has been associated with one thing: DNA. And with good reason. The ability to extract cells from body fluids or tissue and use them to identify a person with near certainty has shaken up criminalistics like nothing before. As technicians have got better at extracting DNA from ever smaller samples, the technology has become increasingly useful, allowing evidence-rich cells to be drawn from traces of sweat, tears, saliva and blood spots a tenth of an inch across. Says Barry Fischer, director of the Los Angeles sheriff department's forensics lab: "You can get good DNA from a hatband or the nosepiece of a pair of glasses."
What's surprising even scientists is the other--even less likely--places they can get it. DNA is generally found only in cells that have a nucleus, which rules out cells in fingernails, teeth and the shafts of hair. What those cells do have, however, is something called mitochondrial DNA, a more primitive form of genetic coding inherited from the mother only. A mitochondrial-DNA sequencing technique developed by anthropologists to help trace human ancestors has been adopted by pioneering crime fighters. Nobody pretends that the new technology is anywhere near as precise as traditional DNA profiling. Nonetheless, later this month an Iowa man, Stephan Zanter, 46, may come to trial for a murder committed in 1989, thanks to mitochondrial testing of two hairs found at the scene.