That's a difficult question. I don't know that we can speak to the frequency with which one runs into fraud in the system. But I think we can speak to the fact that not all labs are created equal, and there must be reasonable quality assurance measures. Even if you have the right person and the sample is appropriately identified, if the test is not done under appropriate conditions, the result of the test will be questionable.
On March 15th, 2012. See this statement in context.