Forensic Physics: Dust and Soil Examination Basics

UGC-NET Forensic Science Unit VII drill on soil and dust examination fundamentals. Covers the five components of soil (mineral matter, organic matter, biological organisms, water, and air), particle-size classification under USDA and ASTM D2487 (sand 2.0-0.05 mm, silt 0.05-0.002 mm, clay below 0.002 mm), Munsell soil colour chart notation (hue/value/chroma), the density-gradient tube principle for comparing soil samples, and stereomicroscopy for morphological examination. Also addresses pH determination, dust composition (mineral grains, fungal spores, pollen, textile fibres, skin cells), and correct packaging protocols (paper envelopes, not plastic, to prevent mould growth).

The Indian context is integrated throughout: ICAR soil taxonomy (Alluvial, Black/Regur, Red and Laterite, Arid/Desert, Mountain) as it applies to scene-soil interpretation, and the role of the Trace Evidence Unit at the Central Forensic Science Laboratory (CFSL) Kolkata in soil and dust comparisons. Murray's Evidence from the Earth (Forensic Geology and Criminal Investigation) and Saferstein's Criminalistics 12th edition are the primary references. Forensic transfer scenarios cover hit-and-run, clandestine body disposal, and footwear evidence linking suspect to scene.

Topics covered:

• Soil components: mineral, organic, biological, water, and air
• USDA particle-size classes: sand, silt, and clay size limits
• Munsell soil colour notation (hue, value, chroma)
• Density-gradient tube: principle and forensic application
• Stereomicroscopy for soil morphology and mineral identification
• Soil pH determination and its evidential use
• Collection SOP: scene sample vs control sample protocols
• Dust composition and forensic significance in trace transfer
• Packaging rule: paper envelope preferred over plastic

Calibrated for first-pass UGC-NET Forensic Science Paper II preparation and NFSU MSc Forensic Chemistry entrance revision. Allow 30 minutes.