A FORENSIC GEOSCIENCE APPROACH OF COMPARING EVIDENCE AND FIELD SAMPLES IN CONNECTION WITH A 23-YEAR-OLD MISSING PERSONS/MURDER COLD CASE

When crimes are committed outside, soil and sediment evidence may be very useful in connecting criminals and objects to the crime scene. This investigation attempts to quantify soil samples taken in connection with an October, 1990, missing persons/murder case and match them to local surrounding areas based on soil characteristics. Two evidence soil samples were collected from behind the victim’s car wheel wells and hitch, a day after he was reported missing. Nine samples were recently collected from two sites of police interest – six from a highland wooded area and three from a lowland floodplain. All soil samples were analyzed by multiple techniques for bulk mineralogy and grain size analysis. After optical study using a 3-90x magnifying microscope, sample splits were wet-sieved at 4 phi to separate the clay/silt fraction. Bulk mineralogy of the clay/silt fraction was determined through X-ray Diffraction (XRD) spectroscopy to compare to known glacial periods in the area and geologic history. Major, minor and trace element constituents of the clay/silt fraction were measured through X-ray Fluorescence (XRF) spectroscopy of both fused disk and pressed powder preparations. Organic matter embedded in the evidence mud also is being studied to help narrow down possible sites. The methods in this study will be used to assist police in their investigation by determining which (if any) of the field locations has more soil characteristic similarities to the evidence samples taken from the victim’s vehicle. Potential matches will be searched using cadaver dogs.