Diatoms are microscopic algae found in fresh water, salt water, and moist terrestrial environments. They are diverse in their form, shape, and structure and can be identified with precision and therefore can be an important analytical tool within a criminal investigation.

Diatom analysis is most often used in cases involving drowning, or prolonged submersion in water, or when proof of contact with water is required.

A comparison of diatom taxa, distribution, and abundance produces a unique environmental profile and provides information on habitat, seasonality, and geographical location. This information can be used to assist in identifying potential sites of drowning or, conversely, can be used to exclude sites where bodies have been recovered.