A window pane at a burglary scene shows radial cracks. Stress marks on these cracks terminate at right angles on the inner face of the pane. Where was the force applied?
- A From outside, because right angles form on the side opposite the impact ✓
- B From inside, because right angles form on the same side as the impact
- C From outside, because right angles always face the impact point
- D Direction cannot be determined from radial cracks alone
Correct answer: A. From outside, because right angles form on the side opposite the impact
Explanation
The 4R rule states that Radial cracks form Right angles on the Reverse side of the force. Right-angled stress marks on the inner face mean the blow came from the outer side. Concentric cracks follow later and show the opposite relationship, so confusing the two crack types is the classic error. Rib (arrest) marks curve toward the side of application on radial fractures, providing a confirmatory check.
Reference: Saferstein, Criminalistics: An Introduction to Forensic Science, 11th ed.
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