They stated, "Every year since 1989, in about 25 percent of the sexual assault cases referred to the FBI where results could be obtained, the primary suspect has been excluded by forensic DNA testing. Specifically, FBI officials report that out of roughly 10,000 sexual assault cases since 1989, about 2,000 tests have been inconclusive, about 2,000 tests have excluded the primary suspect, and about 6,000 have "matched" or included the primary suspect."
The authors continued, "these percentages have remained constant for 7 years, and the National Institute of Justice's informal survey of private laboratories reveals a strikingly similar 26 percent exclusion rate."
If the foregoing results can be extrapolated, then the rate of false reports is roughly between 20 (if DNA excludes an accused) to 40 percent (if inconclusive DNA is added). The relatively low estimate of 25 to 26 percent is probably accurate, especially since it is supported by other sources.
http://www.foxnews.com/story/0,2933,194032,00.html
Also, the supposed incident occured in another country.
Of course, the DNA results don’t have any relevance to those situations where it is agreed a sexual encounter took place, and the only issue is whether the encounter was consensual or forced. Any of these where the rape accusation was false would raise your percentages.
Unfortunately, in these cases the truth is generally known only to the “rapist,” the “victim” and God.