So then I took the rifle personally over to our photo laboratory. In the meantime, I had made arrangements to bring a photographer in especially for the purpose of photographing these latent prints for me, an experienced photographer--I called him in. I received this material in the Justice Building. My office of operations is in the Identification Division Building, which is at 2d and D Streets SW. So I made arrangements to immediately have a photographer come in and see if he could improve on the photographs that were taken by the Dallas Police Department. Well, we spent, between the two of us, setting up the camera, looking at prints, highlighting, sidelighting, every type of lighting that we could conceivably think of, checking back and forth in the darkroom--we could not improve the condition of these latent prints. So, accordingly, the final conclusion was simply that the latent print on this gun was of no value, the fragments that were there. After that had been determined, I then proceeded to completely process the entire rifle, to see if there were any other prints of any significance or value--any prints of value--I would not know what the significance would be, but to see if there were any other prints. I completely covered the rifle. I also had a firearms man---- Representative BOGGS. What do you cover it with? Mr. LATONA. Gray fingerprint powder. Representative BOGGS. What is that powder? Mr. LATONA. It is usually a combination of chalk and mercury, or possibly white lead and a little bit of resin material to give it some weight. Mr. EISENBERG. And you testified earlier that that adheres---- Mr. LATONA. To the moisture that was left by the finger, the fingers or the hands, when it came in contact with the surface. Representative BOGGS. How long will that condition remain? Mr. LATONA. Going from one extreme to the other, it may remain for years; under other circumstances, it may not even last for 15 or 20 minutes. Representative BOGGS. Why the difference? Mr. LATONA. Because of the amount of material which was left and the condition of the material which was left. Basically, the material may be made up of protein material and salt and water--primarily water. If it is totally water, with very little salt or oily material, when the evaporation is effected, then it is complete--there will be nothing left. Representative BOGGS. You mean that it is gone? Mr. LATONA. Right. On the other hand, if there is an oily matter there, we know that latent prints will last literally for years on certain objects. Representative BOGGS. Well, just for purposes of information, if I make fingerprints there on the table, how long would they normally last? Mr. LATONA. I don't know. Representative BOGGS. Well, would there be any way to know? Mr. LATONA. No, sir. Mr. DULLES. It depends on temperature, on the amount of moisture involved? What does it depend on?