Understanding Variations of Soil Mapping Units and Associated Data for Forensic Science

Area of Science:

• Forensic Science
• Soil Science
• Geochemistry

Background:

• Soil samples are valuable in forensic investigations.
• Soil analysis faces challenges due to variability, diverse methods, and complex data.
• Differentiating similar soils is crucial for forensic applications.

Purpose of the Study:

• To assess the utility of various soil properties for differentiating similar soil samples.
• To compare analytical methods for their effectiveness in soil discrimination.
• To explore the potential of soil 'fingerprinting' for forensic casework.

Main Methods:

• Collected soil samples from Fallbrook and adjacent areas in California.
• Characterized soils using gross properties (texture, color, mineralogy) and explicit properties (elemental composition, cation exchange, Fe-oxyhydroxides).
• Employed multiple analytical techniques including chemical extractions, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR).

Main Results:

• X-ray diffraction (XRD) and chemical extractions were more effective than color and texture for sample differentiation.
• Ratios of rare earth elements demonstrated significant utility in distinguishing soils between different counties.
• Analytical approaches varied in their ability to differentiate soils based on land use and geographic origin.

Conclusions:

• Comprehensive soil analysis, including elemental composition and mineralogy, can effectively differentiate similar soils.
• Rare earth element analysis offers a powerful tool for forensic soil discrimination.
• A robust soil database is essential for advancing forensic soil investigations.