New method for processing rape evidence could eliminate crime-lab backlogs

Lab technicians must perform a number of steps to get their results. First, female and male cells must be removed from the swab with a special detergent. DNA from the vast number of epithelial cells from the victim's vagina must be separated from the far fewer sperm cells from the perpetrator. To do this, cells must sit overnight in an enzyme that bursts open the relatively fragile female cells to release their DNA for analysis. After the female DNA is removed, the highly durable sperm cells are burst open using stronger reagents. Once the DNA is extracted, profiles, in effect, are generated for both the victim and the attacker. It is a time-consuming process, one that has been in use for more than two decades.

Later, if a possible perpetrator is arrested, a sample taken from his mouth is analyzed to determine if there is a match with the sperm DNA that was removed from the victim.

Norris' method streamlines the method for separating the male and female DNA fractions, eliminating the need for the overnight incubation while doubling the recovery of sperm cells.

"This new process works extraordinarily well and could be implemented in forensic labs today," Norris said. "Unfortunately, getting labs to adopt a new protocol and getting legal systems to accept a new technology may take several years. In the meantime, the backlog of unanalyzed samples will continue to grow."

Norris noted that forensic science is not simply about proving guilt.

"Forensic science is about finding the truth in a timely manner," she said. "It is about using science to identify the guilty and exonerate the innocent."

Norris presented her findings at a recent meeting of the American Academy of Forensic Science. She will receive her Ph.D. in May this year and hopes to work as a scientist in a state- or federally funded forensics lab. She conducted her research in the lab of U.Va. chemistry professor James Landers.