I have already referred to the ejector marks which are usually present on cartridges fired from self-loading and automatic weapons. In some weapons the firing-pin is used as an ejector, and in others the next cartridge in the magazine or a part of the magazine, and in weapons of these types there will be no ejector mark.
When an ejector mark does exist it is, as a rule, obvious. It may be anything from a thin longitudinal cut to a big gash or indentation in the edge of the case. In some pistols the ejector is rounded and the mark is extremely difficult to detect unless the light catches it at exactly the right angle. So it is unsafe to assume that no ejector mark is present because one was not immediately visible; and in such circumstances a most careful examination of the base of the fired case should be made under a low power of the microscope while the case is slowly rotated through a complete circle so as to ensure the light striking it at every possible angle. It frequently happens that when a fired case is examined thus no ejector mark is visible until suddenly it stands out clearly and distinctly. But when the case is rotated a little more the mark vanishes once again.
The ejector mark, when present, forms a valuable bit of evidence, not only as part of the thumb-mark, but also as a means of orientating the case. For when two fired cartridge cases are being compared it is essential that they should both so be orientated that they must have been the same way up when in the chamber of the weapon. The ejector mark enables this orientation to be effected at once, and if two cartridges are to be compared and both have ejector marks they should both be placed with these marks in similar positions, that is both ejector marks at 3 o'clock, or 9 o'clock. The exact position does not matter provided the same position is utilised for both ejector marks. When this has been done the two cases can be examined with a view to finding other major
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