The identification is based on areas such as this on the bullet and the comparison of the microscopic marks around the entire surface of the bullet which bears individual characteristics.
Mr. Eisenberg. Mr. Frazier, running through the middle of the exhibit there seem to be finer lines on the right-hand side than on the left. Could you explain that, the reason why the lines come out with more detail or that there are more lines on the right side than on the left?
Mr. Frazier. Those marks could be the result of the bullet striking some object after it was fired, or they could be the result of changes having taken place in the barrel.
For instance, even a piece of coarse cloth, leather or some other object could have polished the surface of the metal slightly and left infinitesimal scratches which, when enlarged sufficiently, actually look like marks on the bullet.
Mr. Eisenberg. In making your examination of the bullet, what was the relative attention you gave to the broader lines we see in this picture and the finer lines such as those we have just been referring to?
Mr. Frazier. The broader lines would be more characteristic or they are looked for most, because they change less rapidly than the fine lines. For instance, firing two or three bullets through a barrel could completely erase microscopic marks which would appear as fine lines in a certain area, whereas the coarser lines and grooves on the bullet would be maintained over a series of fired bullets.
Mr. Eisenberg. In evaluating these lines, do you examine the lines individually, or are you interested in their relationship with one another in addition?
Mr. Frazier. It is a combination. You actually examine each mark and each line individually, but it is a mental process rather than a matter of adding one line to another. It is a process of looking at a series of lines and you actually notice that they are composed of round-topped ridges, V-topped ridges, flat-topped ridges, and it is a mental process of looking at the whole pattern rather than the individual marks.
Mr. Eisenberg. All these lines that we are looking at lie within a groove, within one groove, did you say?
Mr. Frazier. Yes; except for the lower portion of the photograph, there is a portion of a land impression showing one rather deep groove running across the bottom of the picture, and a series of grooves shown next to the edge of the land impression.