Fracture pattern analysis of glass found at a crime scene can indicate direction of impact. The distinguishing feature between radial and concentric fractures in terms of rib mark orientation is:

• A Rib marks in radial cracks are perpendicular to the surface from which the force was applied; concentric cracks have rib marks perpendicular to the opposite surface
• B Concentric fractures always appear before radial fractures, providing sequencing information
• C Radial cracks show rib marks at right angles to the EXIT surface (opposite impact); concentric cracks show rib marks at right angles to the ENTRY (impact) surface ✓
• D Glass fragments can be matched by refractive index alone without considering fracture pattern

Explanation

In the RSVP (Radial cracks exit Side, Rib marks Perpendicular on Vertical planes) mnemonic: radial cracks in glass form first on the opposite (exit) surface of the impact; their rib marks are perpendicular to the exit surface. Concentric cracks form later on the same surface as impact (entry surface); their rib marks are perpendicular to the entry surface. This allows determination of impact direction. Radial cracks precede concentric cracks (not the reverse), providing fracture sequence information.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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Written and medically reviewed by the StethoPrep medical team.