Exploring "Who Did It?" with Forensic Science

Image from http://www.phys.ttu.edu/

Since the introduction of fictional detective Sherlock Holmes in the 19th Century, scientific methods have become increasingly important, not only to criminal investigations, but also for such purposes as establishing identity for child support and inheritance issues. A special session at the recent fall meeting of the APS Texas Section, held last October in Austin, TX, highlighted the latest developments in such critical areas of forensic science as DNA testing, fingerprint analysis, and drug and alcohol toxicology.

The session was the brainchild of Manfred Fink, a professor of physics at the University of Texas who teaches a highly popular undergraduate course in forensic science, often to standing-room-only crowds of more than 200 students. "I am limited every time by the size of the classroom," he says, and tries to tie the subject matter into what students have seen on TV, from drug and alcohol toxicology, to DNA testing, to forgery, or how Napoleon died. "O.J. Simpson has done [forensics] a fantastic favor, because it really highlighted the sensitivity of these technologies, so this is a fashionable topic."

DNA testing has been an area of intense public interest ever since its pivotal role in the Simpson murder trial several years ago, and the field continues to advance at a rapid pace. According to Lisa White, a research scientist with the Houston-based Identigene, it is now possible to obtain sufficient DNA samples from the handle of a suitcase, cigarette butts, used Kleenex, bubble gum and soda cans - in fact, from almost anything that comes into close contact with blood, saliva, skin cells or other bodily fluids. "There's just no way to escape DNA analysis anymore," says White, pointing out that the human body sheds 10,000 cells day.

Identigene specializes in laser-based technology for all kinds of DNA analysis, including paternity testing, criminal testing, forensic testing, and family reconstructions. DNA analysis has been used to identify body parts retrieved in the aftermath of the recent Egyptian Air disaster, or body parts scattered from graves in cemeteries during the recent floods in North Carolina, and reassemble them. The company's latest innovation is a DNA microarray called APEX, capable of identifying 70 different genes with nearly absolute certainty. As for the Simpson acquittal and the subsequent controversy surrounding DNA evidence introduced in court, "The science itself is hardly ever questioned," says White. "When defense attorneys object to DNA evidence, it's not the actual results they're fighting, it's how someone gathered the evidence."

Roland Menzel, a professor at Texas Tech University and director of its Forensics Science Center, discussed techniques for fingerprint analysis, opening with a sample obtained from the days of the Civil War, using one of the most primitive methods: laser detection of the inherent fluorescence of fingerprint residue. In addition to occasional casework consulting in forensics, Menzel is developing a new technique that involves tagging fingerprints with photoluminescent semiconductor nanocrystals, which, because they have long luminescent lifetimes, can enable time-resolved imaging to get rid of unwanted backgrounds for a clearer image of the print.

Also featured at the session was W. Ginn, Jr. of the Texas Department of Safety Crime Laboratory, who described how drug and alcohol toxicology methods have helped law enforcement personnel locate and confiscate various contraband substances, such as heroin, cocaine and marijuana. Even standard spectrometry techniques have improved to the point where analysts can now test for 160 different drugs in the body simultaneously, from a single drop of blood, and within two minutes, according to Fink.

However, while the physics and technology for better and more accurate forensic analysis is there, Fink emphasizes that forensic methods are useful primarily if one has a target subject to which one can compare the results. Also, as the LAPD discovered in the Simpson trial, there must be immaculate handling of the collection of the sample to be analyzed in order for the results to be useful as evidence in courts of law. Menzel conducts the occasional workshop for law enforcement employees to train them in various aspects of forensic analysis, including the correct procedure for collecting samples. "Even the most modern technology cannot help you if the sample isn't handled correctly," says Fink. "So we must educate the rest of the world."