Mr. Cunningham. To remove possible dirt from my hands. I washed my hands. The gun was then wiped off with dilute HCl to get rid of any deposits already on the gun, and I fired it in our bullet-recovery room, four times—and then after firing I opened it up and ejected the cartridge cases into my hand, as I showed you earlier today. The amount of residue that you pick up on your hands from ejection of the cartridge cases was in my hand at the time.
I then, under ideal conditions naturally, went back and had paraffin casts made of my hands and these were treated with a solution of diphenylbenzidine.
The results of this examination were that we got a positive result on both casts, front and back. Many reactions in this area where I had ejected the cartridge cases in my hand were noted.
Mr. Eisenberg. By the way, you testified this morning that many common substances will produce a positive reaction to the nitrate test, so-called paraffin test.
Will the handling of an unclean weapon also produce a positive reaction?
Mr. Cunningham. Just as much as firing it will. That is what makes this test so unreliable. Handling a recently fired weapon, that is covered with residues—you would get just as many oxidizing agents in the form of nitrates and nitrites on your hands as you would from firing it and in some cases more—especially up here and around here you would.
Mr. Dulles. Does the time between the tests, between the firing and the test, make very much difference, within a few hours?
Mr. Cunningham. If the residues are on the skin they will react. In other words, if the material has been washed off completely, then you are all through, but if it remains on the skin or is imbedded in the pores of the skin it would still react, but so will so many other things.
Mr. Eisenberg. Just to review for a second your testimony this morning, in the experiments that the FBI ran, a revolver or automatic pistol were used as opposed to rifles, as I recall it?
Mr. Cunningham. Yes.