WHILE FORENSIC SCIENCE HAS MADE EXTENSIVE USE OF THE POSSIBILITIES OFFERED BY BOTANICAL CLASSIFICATION, IT HAS NOT YET TAKEN SIMILAR ADVANTAGE OF THE POSSIBILITIES AVAILABLE IN THE FIELD OF ZOOLOGY. THE MICROFAUNA OF SOIL SAMPLES ARE EXTREMELY INTERESTING FROM A FORENSIC SCIENCE STANDPOINT BECAUSE SOIL CONTAINS A VAST NUMBER OF DIFFERENT SPECIES OF MICROFAUNA AND EACH TYPE OF TERRAIN HAS A UNIQUE CHARACTERISTIC CONFIGURATION. ALSO, ANALYSES CAN BE PERFORMED ON VERY SMALL SAMPLES (1 OR 2 G.) BECAUSE OF THE ABUNDANCE OF THIS TYPE OF FAUNA. THERE IS A CLASS OF TERRESTRIAL FAUNA--PROTOZOA RHIZOPODEA TESTACEA--WHICH IS A UNICELLULAR ANIMAL INVISIBLE TO THE NAKED EYE AND WHICH COULD BE CALLED THE 'PLANKTON' OF NONAQUATIC MICRO-ORGANISMS. BECAUSE OF THEIR SIZE, THEIR BIOTYPE, AND THE FACT THAT THE SHELL REMAINS AFTER THE ANIMAL DIES, TESTACEA ARE VERY GOOD SUBJECTS FOR QUANTITATIVE AND QUALITATIVE FAUNA STUDIES CONDUCTED FOR CRIME INVESTIGATION PURPOSES. BECAUSE OF THEIR LIFE CYCLE AND BECAUSE THEIR BIOTYPE IS CHARACTERIZED BY A LARGE NUMBER OF SPECIES, THESE PROTOZOA SERVE AS BIOLOGICAL, GEOLOGICAL, AND ECOLOGICAL INDICATORS. ALSO, THEIR BIOCOENOSES FORM WHAT MIGHT BE CALLED 'ECOLOGICAL NICHES' THAT ARE HIGHLY CHARACTERISTIC OF PRECISE LOCATIONS. THE BASIS FOR CLASSIFICATION IS THE FORM OF THE SHELL, WHICH SHOWS SPECIFIC HEREDITARY CHARACTERISTICS. THERE ARE 1,500 KNOWN SPECIES OF TESTACEA, AND THESE HAVE BEEN CATEGORIZED INTO 16 FAMILIES; ONLY 120 SPECIES, HOWEVER, ARE FOUND IN THE SOIL. BY MATCHING THE SHELL CHARACTERISTICS OF TESTACEA TAKEN FROM SOIL AT A CRIME SITE WITH TESTACEA SHELL PRESENT IN SOIL SAMPLES FROM SUSPECT'S SHOES, FOR EXAMPLE, POTENTIALLY SIGNIFICANT CIRCUMSTANTIAL EVIDENCE CAN BE OBTAINED. THE TECHNIQUE HAS BEEN USED IN AT LEAST ONE INSTANCE IN BELGIUM TO CONVICT A SUSPECT OF RAPE AND MURDER. TABULAR DATA, PHOTOS, AND BIBLIOGRAPHY ARE PROVIDED. (KBL)