As justice races to keep pace with technology, new questions about how evidence is obtained are coming into play, reports McClatchy Newspapers.
Trace DNA – tiny amounts of genetic material – is saddled with complications, creating confusion in and out of courtrooms and prompting a new realization: Forensic science can’t always lead to clear-cut results.
These samples, known as low template or low copy number DNA, often degrade in quality once they’re replicated for testing. Mixed sample DNA presents similar problems because it contains genetic material from two or more people, and each must be isolated before being matched.
Then there’s touch DNA, the sort of infinitesimal residue that’s left on the trigger of a gun, for example, or a ballpoint pen. It may be as small as three human cells. This DNA can be replicated and tested, but a conclusive match can be tough to find.
Frederick Rench, a defense attorney based in Clifton Park, N.Y., spent 18 months learning the ins and outs of DNA testing and its complications while defending a client.
“That’s just how complex this stuff is,” he said.
How and when to use this evidence is controversial.
“This is something we are trying to figure out ourselves,” said Paul Cates, communications director for the Innocence Project, a nonprofit legal group that relies on DNA evidence to exonerate wrongfully convicted people. “We realize that there’s a lot of discussion about (low template number DNA) in the scientific community and we are doing our own research to figure out where we are on this.”
More easily tested is a single strand of hair, a mouth swab or blood from a single source. They are the sorts of high template number DNA samples that are often the stuff of popular courtroom dramas. Reliable, definitive results are routinely expected; there’s plenty to test and normally only one set of DNA. And the testing procedures are pretty standard.
“Any qualified lab analyst could follow these procedures and give results that wouldn’t be challenged,” said Brian Meehan, a professor of forensic biology at Ohio Northern University and the director of forensics at IntelliGENTETICS, a DNA testing lab.
It’s the low template and mixed sample DNA evidence that has prompted debate in courtrooms from New York to Indiana, as defense attorneys and prosecutors quarrel over evidence admissibility, generating appeals and overturned convictions.
While not totally bulletproof, the computerized DNA testing is gaining acceptance. The repercussions could be significant. How, one might ask, can a defense attorney cross-examine a software system?
Rench said it’s a marked difference, and he’s wrestling with it himself. He only hopes that better evidence will lead to more justice.
“And who can argue with that?” he said.
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9 months ago