I wonder why the FBI did not do a follow-up on the NAA tests on the 7 test shooters to test for false negatives.
Have 7 other marksmen shoot, then wash their faces, then take a paraffin test to see whether the NAA would be positive or negative.
I guess the FBI did not have a statistician or probability modeller take a look at the experimental set up or maybe they just didn't want to know the answer.