Conjunctive use of synchrotron X-ray diffraction and Rietveld refinement in Fe-oxide clays for forensic applications

Area of Science:

• Geochemistry
• Mineralogy
• Forensic Science

Background:

• Soils possess unique properties enabling differentiation and association with crime scenes.
• Clay fraction mineralogy and structure offer distinct characteristics detectable by advanced analytical techniques.

Purpose of the Study:

• To compare the discriminative power of Fe-oxide concentrated clay samples from the same soil class but different parent materials.
• To evaluate the effectiveness of Rietveld refinement using conventional and synchrotron X-ray diffraction for soil discrimination.

Main Methods:

• Clay samples were concentrated for iron oxides, removing kaolinite and gibbsite.
• Rietveld refinement was applied to analyze mineralogical composition using conventional and synchrotron X-ray diffraction data.
• Twelve samples from simulated crime scenes developed on claystone and granite were analyzed.

Main Results:

• Rietveld refinement provided detailed crystallographic data for sample discrimination based on provenance.
• Synchrotron radiation enhanced quantitative (crystallite size, mineral content) and qualitative (mineral identification) analysis.
• The methods successfully discriminated samples from different and even the same geological origins.

Conclusions:

• Rietveld refinement with X-ray diffraction, especially using synchrotron radiation, is a powerful tool for forensic soil analysis.
• The technique offers high resolution for discriminating soil samples based on their geological source.
• This method has significant potential for application in criminal investigations requiring soil comparison.