Sunday, July 20, 2008

How reliable is DNA in identifying suspects? - Los Angeles Times

How reliable is DNA in identifying suspects? - Los Angeles Times:
"State crime lab analyst Kathryn Troyer was running tests on Arizona's DNA database when she stumbled across two felons with remarkably similar genetic profiles.

The men matched at nine of the 13 locations on chromosomes, or loci, commonly used to distinguish people.

The FBI estimated the odds of unrelated people sharing those genetic markers to be as remote as 1 in 113 billion. But the mug shots of the two felons suggested that they were not related: One was black, the other white. ..."
Conventional wisdom has suggested for many years that DNA testing is as close to objective truth as you can get. Even when questions get raised they usually involve contamination or faulty procedures. It appears that a closer look needs to be taken at how these tests are employed as evidence.

It seems that nine genetic markers were considered sufficient in the past for establishing DNA matches, although many states are now using 13 markers. One of the cases in this article involved DNA from a crime committed 20 years ago, and such older samples may not have been tested for any more than nine markers.

Of particular concern are the allegations in this Los Angeles Times article that the FBI attempted to suppress these findings and made threats to states performing what came to be known as an "Arizona search" that their access FBI resources could be cut off. While such sanctions have not yet been taken, further searches have revealed a number of similar matches between unrelated people around the country.

This is a scientific issue, and must be dealt with using the open methods of science. It does much damage to the cause of justice if the custodians of DNA databases try to prevent the sorts of comparisons described in this article.

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