recombine into silver chloride and sodium nitrate. We know that silver is sensitive to light. So that material, after it has been treated with the silver nitrate solution, is placed under a strong light. We utilize a carbon arc lamp, which has considerable ultraviolet light in it. And it will immediately start to discolor the specimen. Wherever there is any salt material, it will discolor it, much more so than the rest of the object, and show exactly where the latent prints have been developed. It is simply a reaction of the silver nitrate with the sodium chloride.

That is all it is.

Mr. Eisenberg. Do you frequently find that the silver nitrate develops a print in a paper object which the iodine fuming cannot develop?

Mr. Latona. Yes; I would say that is true, considerably so. We have more success with silver nitrate than we do with the iodine fumes.

The reason we use both is because of the fact that this material which is exuded by the fingers may fall into one of two main types—protein material and salt material. The iodine fumes will develop protein material. Silver nitrate will develop the salt material.

The reason we use both is because we do not know what was in the subject's fingers or hands or feet. Accordingly, to insure complete coverage, we use both methods. And we use them in that sequence. The iodine first, then the silver nitrate. The iodine is used first because the iodine simply causes a temporary physical change. It will discolor, and then the fumes, upon being left in the open air, will disappear, and then the color will dissolve. Silver nitrate, on the other hand, causes a chemical change and it will permanently affect the change. So if we were to use the silver nitrate process first, then we could not use the iodine fumes. On occasion we have developed fingerprints and palmprints with iodine fumes which failed to develop with the silver nitrate and vice versa.

Mr. Eisenberg. Now, Mr. Latona, looking at that bag I see that almost all of it is an extremely dark brown color, except that there are patches of a lighter brown, a manila-paper brown. Could you explain why there are these two colors on the bag?