Physical Evidence & Holes in Glass

Topic# 1

In the section about the identification and significance of physical evidence, the text asserts that simple rules cannot be devised for defining what constitutes a thorough and foolproof analytical scheme. Why not? 100 words

 

Topic# 2

Why is it difficult to determine just from the size and shape of a hole in glass whether it was made by a bullet or by some other projectile? 100 words