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Recent admissions by the FBI involving data errors in calculating DNA probabilities are challenging the infallibility of DNA evidence, a science with a longstanding reputation of as the forensic gold standard.

Prosecutors and bureau officials say the mistakes will have a minimal effect on criminal cases, but the real impact of the revelations in courtrooms across the country remains to be seen.

Vince Figarelli, the Arizona Department of Public Safety's crime-lab superintendent, stressed that the discrepancies do not amount to mismatching a DNA profile with a certain suspect.

Rather, he said, the corrected information alters only the likelihood that a DNA profile will be found in a certain population. This could be the difference between finding a matching crime-scene profile in one case out of 110 quadrillion, versus a corrected probability of one case out of 1 quadrillion.

The new information could be applied retroactively to court cases by defense attorneys, and Figarelli said his lab is mapping out how it will evaluate "thousands" of historical Arizona cases.

While a difference between, say, 1 sextillion and 1 quintillion...