Q. Mr. Shaneyfelt, what is the basis of your statement, the theoretical basis of your statement, that every camera with this type of back aperture arrangement is unique in the characteristics of the shadowgraph it makes on the negative ?

Mr. SHANEYFELT. It is because of the minute variations that even two cameras from the same mold will have. Additional handwork on cameras, or filing the edges where a little bit of plastic or a little bit of metal stays on, make individual characteristics apart from those that would be general characteristics on all of them from the same mold.

In addition, as the film moves across the camera and it is used for a considerable length of time, dirt and debris tend to accumulate a little--or if the aperture is painted, little lumps in the paint will make little bumps along that edge that would make that then individually different from every other camera.

Q. Is this similar then to toolmark identification ?

Mr. SHANEYFELT. Very similar; yes.401