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Testing, Testing 

Local Matters

Burlington police spent two weeks tracking Laura Winterbottom's murderer. They found him, ultimately, in a laboratory.

When authorities arrested an Old North End resident last week and accused him of murdering and sexually assaulting 31-year-old Winterbottom, it was DNA evidence that connected him to the crimes. Police said bodily fluids recovered from Winterbottom's car and body matched a sample taken from 33-year-old Gerald Tyrone Montgomery, a previously convicted sex offender. Montgomery has pleaded not guilty to both charges.

As a result of TV crime shows and highly publicized celebrity trials, most people these days have a basic understanding of DNA evidence -- what it is and how it's used in criminal cases. But a visit to Vermont's state forensic lab proves that the DNA testing process is more complicated than it looks on TV.

The state's only forensic crime lab is located behind a metal door on the third floor of the Department of Public Safety building in the Waterbury state offices complex. White walls and a gleaming tile floor give the lab an antiseptic appearance, accentuated by the strip of sticky paper that serves as a welcome mat to the DNA analysis room. Lab director Eric Buel explains that the paper helps to reduce the amount of dust in the tight space.

When police collect a sample from a crime scene, he says, they take it first to the serology department, where technicians determine, for example, if stains on a shirt are blood or chocolate sauce. If the sample contains DNA, it's liquefied and brought to the analysis room. Technicians there use pen-like injectors called pipettes to transfer the DNA-filled fluid to clear plastic tubes half an inch long and an eighth of an inch in diameter.

They run the samples through three machines. The first instrument, a "Real-time PCR," determines if there's enough DNA in the sample to test. The second, a thermocycler, replicates the DNA strands, and embeds fluorescent dyes that will enable the third machine -- the genetic analyzer -- to prepare a profile.

It's a lengthy process. "DNA analysis, unlike on 'CSI,' takes time," says Buel. As he displays the machinery, Joseph Abraham, a forensic chemist, runs a sample through the genetic analyzer. Unlike the genetic analyzer on "CSI," Abraham's machine doesn't have lights that illuminate the samples.

Inside the analyzer, a tube extends into the DNA sample, and sucks up fluid into another tube the width of a human hair. Lasers penetrate the tube to search for fluorescent dyes. Abraham stands in front of a computer linked to the machine, which interprets the data and produces a multicolored graph that is indecipherable to non-experts.

Under the best circumstances, Abraham says, the lab can produce a profile in three days. But Buel says that may extend to a week; he declines to discuss the timetable in the Winterbottom case. Homicides are obviously the first priority, but if the machine is mid-analysis, it has to finish before the next sample can be introduced.

And Buel notes that the genetic analyzer is sometimes temperamental. "If the instrument breaks and we have to call a service rep," he says, "they're out of Boston."

Once the profile emerges from the analyzer, a technician determines whether it contains enough information to deliver an accurate match. A second analyst double-checks the report. Then the profile is checked against the genetic profiles of identified suspects, and against the Vermont's Combined DNA Index database. If a match is found, technicians test the original sample to be sure they got an accurate reading. They'll take another sample once the suspect is in custody, from a cheek swab or a blood draw.

Buel says there are multiple checks built into the system. That's crucial, because the likelihood of a false match is slim. "We give statistics in the billions and trillions," he says. "Statistically, it's terrific evidence."

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About The Author

Cathy Resmer

Cathy Resmer

Cathy Resmer is a former staff writer and currently an associate publisher at Seven Days, and is one of the organizers of the Vermont Tech Jam. She's also the Copublisher and Executive Editor of Kids VT, Seven Days' free monthly parenting publication.


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