Soil — it's more than just dirt to be washed away.
Soil samples taken from a crime scene can tell investigators a lot about a suspect, victim and their relationship to one another. By closely examining the characteristics of particles and pieces in each soil sample, it is sometimes possible to associate those characteristics to a specific location. Analysis of soil samples taken from a shoe can pinpoint where the shoe has been. And, analysis of footwear, clothing and tires can place a suspect or victim in a particular location. (See the Fabric link on examining threads and fabrics found at a crime scene.)

The first thing investigators look at when examining soil is what kind of particles make up the soil. The 3 most obvious types of particles to observe in the soil are:

Sand, hard grain size pieces of quartz mineral

Non-sand Minerals are often clumps and vary in size from minute barely visible to large gravel sized clumps, this also includes gravel and smal stones that are not sand

Organic, are pieces that come from something that was alive. It could be pieces of grass, stem, leave, dung (poop), or body parts