Forensic Soil Science class teaches students about crime scene analysis

Story and Photos By: Beth Ann Luedeker

Contact: Dr. Jacqui Aitkenhead-Peterson,  jacqui_a-p@tamu.edu

Forensic soil lab

Dr. Jacqui Aitkenhead-Peterson explains evidence collection to her Forensic Soil Science class at the mock crime scene. (Photo by Beth Ann Luedeker)

Scattered bones found outside the Heep Center this month, were quickly surrounded with crime scene tape to prevent disturbance of the evidence. The “crime scene” was part of an ongoing investigation in the Forensic Soil Science class taught by Dr. Jacqui Aitkenhead-Peterson.
Forensic Soil Science (FIVS/SCSC 401) teaches soil science applicable to forensic science.  Students learn to assess soil color, particle size analyses, particle shapes and size, the natural assemblages of soil (physical, biological and chemical) and unusual anthropogenic assemblages that might be found in a soil sample.

students making grid

Students create a grid over the mock crime scene to accurately record the locations of the scattered bones and other evidence. (Photo by Beth Ann Luedeker)

A major part of the course is the “Muddy Boots” case,” a fictitious scenario in which a graduate student is reported missing. Each student provides a soil sample from their “alibi location” during the summer, collected to a depth of 2.54 – 5.00 cm.  3 sets of footwear are also “retrieved”, each containing either alibi soil, reference soil or crime scene soil.
“One objective is for the students to see how soils from across the nation differ, and the discriminatory power of soil chemistry to match one of the pairs of boots to the crime scene,” Peterson said.
When the scattered remains appear outside the Heep Center, the students process the scene in the same manner as taught to Law Enforcement at the Sam Houston State University Donor facility.  They first create a grid over the area, and then collect and record evidence in each grid, including  soil samples taken to a depth of 2.54 cm for comparison to the “muddy boots”.

student using EC probe

The students use probes to test the electrical conductivity of the soil to determine if decomposition products are present. (Photo by Beth Ann Luedeker)

The students also collect soil samples from the potential area of entry to the crime scene, and reference soils (soils of the same soil series as the crime scene).
“Electrical conductivity (EC) probes are used to record EC values in each grid square of the crime scene and also by hidden evidence items presumably belonging to the victim,” Peterson said. “Where the EC value is highest, this denotes a potential cadaver decomposition island (CDI).”

Students mark and record the location of each bone and other pieces of evidence in the mock crime scene as part of the forensic soil science class. (Photo by Beth Ann Luedeker)

Increased electrical conductivity is an indication of deomposition. Where this is noted, the students collect a 15 cm soil core as evidence. Peterson explained that 15 cm is the depth most useful for estimating post-mortem interval.
“All soils collected will be used for further chemical analyses along with statistical analyses to determine which pair of muddy boots was at the crime scene,” said Peterson.

students in class

Students in the Forensic Soil Science class learn to collect evidence and follow the same procedures used by law enforcement personnel. (Photo by Beth Ann Luedeker)

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