A University of Virginia forensic chemist has developed a method for handling rape evidence that reduces part of the DNA analysis time from 24 hours to as little as 30 to 45 minutes.
The method also improves the sperm cell recovery rate by 100 percent.
If adopted by forensic labs and accepted by courts the time-efficient method, developed by Jessica Voorhees Norris, a Ph.D. candidate in forensic chemistry at U.Va., could potentially reduce the backlog of evidence asking for analysis, just within a few months.
"There is an overwhelming demand for DNA analysis of sexual assault evidence, but laboratories have neither the funding nor the manpower to handle the caseload in a timely manner. Juries have come to expect DNA evidence in sexual assault cases, but forensic labs are not able to perform in a timely and efficient manner due to limitations in the currently used technologies," said Norris.
In case a woman reports being sexually assaulted, a sample is taken from the vagina with a cotton swab for sending to the forensic lab. The DNA analysis in high-profile cases is done immediately, which also involves overnight incubation. On the other hand, in routine cases the sample is put into storage for as long as a year and is not analysed till the case approaches a court date, often causing the sample to degrade.
Getting the results in lab involves a number of steps wherein first the female and male cells are separated. This requires an overnight incubation period. Once the DNA is extracted, profiles, in effect, are generated for both the victim and the attacker. This two decades old practice is quite time-consuming. And later, the DNA sample is matched with the perpetrator's DNA taken from his saliva.
However, Norris' method simplifies 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," said Norris.
Norris presented her findings at a recent meeting of the American Academy of Forensic Science.