This is a difficult subject to comprehend due to the statistics involved. As such, it is often, when dealing with questions on the subject in court, glossed over with such comments as 'statistically it can be shown, but as I am not a statistician' or ' empirical studies have shown' or even ' a match is one which exceeds the best known non-match'.
But, how large does an empirical study have to be before it can be determined that a match between two bullets is beyond reasonable doubt? Does an empirical study with one weapon type necessarily have any bearing on other weapon types? And, even more difficult to quantify, what is a best known non- match and how many require observation before one can be recognized?
All are crucial questions and, if not correctly answered, or for that matter correctly handled by the prosecution or defence, they could lead to misrepresentation of evidence or even the witness being unnecessarily discredited.
These matters do involve quite difficult statistics, and such mathematical concepts can become very complex. This chapter will attempt to show why no match, no matter how good, will ever be 100% perfect. It will also attempt to handle the statistical side as simply as possible, allowing even the non-mathematically minded to grasp the basics of the subject.
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