by Michael Dymmoch
I was invited to come to Minnesota recently, to do an interview with The Minnesota Crime Wave. Carl Brookins, William Kent Krueger and Ellen Hart are exemplars of what makes the mystery community a community—gracious, generous and intelligent. Damn fine writers, too. Minneapolis/St Paul is a seven hour drive, so Carl offered to put me up after the interview. Next day, he gave me a tour of the Twin Cities, a terrific lunch, and a ride to the Mystery Writers of America meeting at Once Upon a Crime.
MWA’s guest speaker was Ann Marie Gross, Technical Leader of St Paul MN’s Bureau of Criminal Apprehension (BCA). The FBI recently honored her for her work with DNA.
Ms. Gross told us that crime scene evidence is brought to the BCA by submitting agencies or sent in via US mail or FedEx. In the biology section, a visual inspection is performed for trace (hairs, fibers, etc.) as well as stains. A serological exam reveals whether blood, semen, saliva or other body fluids are present on clothing or other items; presumptive semen stains are examined microscopically for the presence of sperm. Blood and semen are commonly known to yield DNA, but DNA can also be recovered from licked envelope flaps, and the sweat found on hat bands, shirt collars and garment underarms. Individuals may also leave enough skin cells on a gun grip or trigger to prove they’ve handled the weapon—something convicted felons often learn to their dismay.
The root of a hair is the only part containing nuclear DNA—the type required for positive identification of an individual (or his identical siblings). A hair shaft can, however, yield mitochondrial DNA (mtDNA) which, as Barbara D’Amato recently pointed out, is inherited from the maternal line and shared with non-identical sibs. MtDNA is most often used to identify unknown human remains, since there are usually more standards—DNA from relatives—for comparison. (The Chicago Sun-Times reported Friday that the remains of Nicolaus Copernicus, the first astronomer to recognize that the earth orbits the sun, were recently identified by comparing DNA from his skeleton with a hair found in one of his books.) All 50 states have laws requiring convicted offenders to provide DNA samples, and the national DNA database, CODIS (Combined DNA Identification System) has 5 million on file.
After the DNA is isolated and amplified at the BCA, it’s analyzed by a machine (ABI 310) that runs 24 hours a day, five days a week. The process, which once took seven weeks and required a dime-sized blood sample, can now be done with a sample the size of a pen tip and completed in 30 minutes. Evidence turnaround time at the lab is two months—from receipt to report. Public safety cases (e.g. serial rapists) are moved to the head of the queue with scientists working late and on weekends.
BTW: Murder & Mayhem in Muskego was even better than Alison Janssen predicted in her November 7 guest blog. Thanks to Muskego librarian Penny Halle and Jon and Ruth Jordan for a terrific conference.