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DNA sequence identify a specific person (except in cases of identical births). Basically, says Prevett, the process involves extraction, quantification, amplification, and interpretation. According to the DNA Handbook, forensic work now uses polymerase chain reaction (PCR) processes as the standard DNA typing system. Prevett says it allows scientists to quickly locate particular areas of DNA, "the molecular equivalent of finding a needle in a haystack." When that needle is found, it can be used to pinpoint the person from whom it came. But, experts caution, DNA can be used not only for helping prove a case against someone, but also for ruling out suspects. As the technology has progressed since its usage began in British courts almost 25 years ago, it has been used to exonerate the wrongly convicted. Everything must be seen in the context of the case. "Semen left upon the body of an assault victim connotes not only timing but that its owner was the perpetrator of the sexual assault," Prevett says. "My semen is found in a woman who is dead," he illustrates. "'Aha!' Then it turns out she's my girl- friend. If it turns up in a woman I don't know, then it has meaning." Which brings us back to the indigo. What if the mystery semen is on a pair of blue jeans? Well, explains UBC engi- neering physicist Andre Marziali, the indigo inhibits the PCR process. That's where the new SCODA (synchronous coefficient of drag alteration) concentra- tion method comes in. It's the brainchild of Marziali and his team. He says the SCODA process can reject contaminants such as indigo, acids from environmental sources, soil, and blood. The clean DNA then moves into the PCR process for typ- ing. "We can reject between a hundred to a thousand times more [contaminants] than other processes," he says. Marziali has been working in DNA research at both UBC and California's Stanford University for years, but says he did not set out to find the process. Rather, it's an idea that came up over coffee with colleague Lorne Whitehead, who posited the initial mathematical formula for the concept. But, Marziali chuckles, there was no eureka moment. "It was a discovery," he says. The team's method employs a DC ntitled-1 1 GIFFIN KOERTH SMART FORENSICS How you look at it matters There's more to smart forensics than superb science and a knack for solving puzzles. Here's our view on what makes a preferred partner. 360° Services The real world is complex. Forensic files mirror that complexity. So should forensic services. Unshakeable Science To win more cases and settle to greater advantage, do the forensics first. Clear Communications Your case is not compelling unless it's clear – and the telling holds up under fire. Collaborative Work Style Today's cases are simply too involved for people to work on their own. Vital Culture People make a difference – especially when you make a difference for them. If you see it the way we do, give Chris Giffin a call at 416.368.1700. Giffin Koerth is located in downtown Toronto at 40 University Ave., Suite 800, M5J 1T1 giffinkoerth.com FORENSIC ENGINEERING • FORENSIC ACCOUNTING • COMPUTER FORENSICS www. C ANADIAN Law ye rmag.com NO VEMBER / DECEMBER 2009 39 1/21/09 2:28:57 PM