• Direct Detection: The probe detects fatty acids preserved in the soil, enabling accurate identification of human remains. 

• Precision Location: Provides precise burial site locations, reducing the need for extensive excavation and conserving resources. 

• Effective Combination: Integrates seamlessly with other detection methods, like human remains detection dogs (HRDs) and Ground Penetrating Radar (GPR), for a comprehensive investigative approach. 

• Minimally Invasive: Preserves the integrity of the investigation site with minimal disruption while delivering fast, reliable results. 

On June 12, 2024, S4 Mobile Laboratories was granted a patent for its groundbreaking soil probe technology, marking a major advancement in soil spectroscopy. The patent protects S4's unique fiber-optic soil probe design, which enables a compact, efficient approach to subsurface soil analysis. 

S4’s Subterra technology utilizes an innovative, all-fiber-optic probe design, only half an inch in diameter and over a meter long. Light is delivered through fiber optics to the probe tip, and the reflected light is analyzed by spectrometers to measure various soil properties. With all active components, including the light source and measurement tools, remaining above ground, the probe is smaller, highly mobile, and easy to deploy. 

The Subterra probe is highly compact, weighing approximately 135 pounds and portable enough for single-person operation, even in confined spaces. Its above-ground active components and all-fiber-optic construction make it much thinner and easier to insert into the soil. The design also includes thermal expansion compensation, ensuring consistent performance in diverse outdoor temperatures. 

The Subterra probe serves multiple applications, including: 
 

• Agriculture: Provides in situ soil property measurements, including soil organic carbon, to enhance crop management. 

• Environmental Monitoring: Enables accurate soil composition analysis for environmental assessments. 

• Forensic Investigations: Detects human remains and identifies burial sites with minimal disturbance. 

The probe, with a diameter of just 13 mm and a reach of up to 90 cm, does not add or remove soil during insertion, which helps preserve the site. It minimizes disturbance by limiting insertion points and halting penetration upon encountering obstacles such as stones, roots, or bones, preserving fragile remains. 

The Subterra Grey probe's accuracy is not defined by traditional false positive or false negative rates due to several factors: 
 

• Complex Site Histories: Investigative sites, particularly those connected to historical or sensitive investigations, often involve complex land-use histories and decades-old burials. Investigators typically use the Subterra Grey in conjunction with other tools, such as GPR and cadaver dogs, for comprehensive analysis.  

• Varied Burial Conditions: Graves vary in age, environmental conditions, and other factors, making standard accuracy measures difficult to establish. 

• Data Sensitivity: Data from First Nations sites and similar sensitive locations are usually kept confidential, unless permission is given to share the data, which limits comprehensive accuracy studies.
   

Field tests in Canada and the U.S. have shown that the Subterra Grey consistently provides valuable results in these contexts. 

The Subterra Grey identifies unmarked graves through two primary measurements: 
 

• Soil Hardness Measurement: It records the force needed to insert the probe, helping identify areas of softer soil indicative of refilled graves. This method has proven effective in detecting graves over a century old. 

• Detection of Fatty Residues: The probe utilizes infrared light to detect fatty residues left by decomposed remains, providing data on the spatial distribution and depth of remains. These residues can persist for decades or even a century. The Subterra Grey locates remains buries underground, but does not distinguish between human remains and similar-sized animals. 
   

In summary, the Subterra Grey can detect both the refilled grave and any remaining biological material, as well as pinpoint the depth and location of burials. 

With a diameter of 13 mm and a penetration depth of up to 90 cm, the probe is minimally invasive. It neither adds nor removes soil during insertion. To further reduce the risk of damaging any fragile remains, limiting the number of insertions and stopping when evidence is sufficient to confirm a burial site is recommended. 
 

The probe’s insertion force can be adjusted to a lowest level (e.g., 250–300 lbs) which is needed to reach target depths. Upon encountering obstacles like stones, roots, or bones, it comes to a stop which minimizes damage to the grave contents. However, there is still a minor risk of damage to smaller or more delicate remains. 

The Subterra Grey probe only detects materials it directly contacts, as soil is opaque to infrared light. Tests with animal burials show that remains tend to stay within the grave's outline, even if they spread slightly over time. 

Certain conditions can produce readings similar to human remains: 
 

• Moved Human Remains: If a body decomposed at one location and was later moved, the probe may detect the "grave soil" remaining at the original site.  

• Animal Remains: Signals from animal remains are similar to those from comparably sized humans. However, wild animals are usually lean and not commonly buried, minimizing potential confusion. 

• Kitchen Waste: Buried kitchen fats, such as from a deep fryer, could produce similar signals, though they may be distinguishable by the spatial distribution of the signals.