A forensic scientist examines broken glass fragments from a hit-and-run scene. Refractive index (RI) measurement by the oil immersion method shows the crime scene glass has an RI of 1.5230 ± 0.0002 and the suspect vehicle's headlight glass measures 1.5228 ± 0.0002. The MOST appropriate interpretation is:

• A The glass cannot be from the same source because the RI values differ
• B RI measurement alone is sufficient to prove the glass is from the suspect vehicle
• C The measurement uncertainty makes this evidence inadmissible
• D The glass could share a common origin as the RI values overlap within measurement uncertainty ✓

Explanation

Refractive index matching within measurement uncertainty is interpreted as inability to exclude a common source — the glass could have originated from the same production batch or the same broken object. The RI values 1.5230 ± 0.0002 and 1.5228 ± 0.0002 overlap, meaning they are analytically indistinguishable. This is supportive but not conclusive proof; elemental analysis (LA-ICP-MS) provides additional discrimination. A numerical difference within uncertainty does not exclude common origin, and the evidence is admissible as part of a wider body of trace evidence.

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.