here are many applications for GPR in the field of law enforcement and security. One common application is to locate forensic evidence at a crime scene. In these cases, evidence is usually a body, weapon or a container which may contain drugs, money or documents. Many law enforcement agencies worldwide are using GPR to aid in locating this type of evidence.
Earlier this year, the Portuguese Criminal Police hosted a CSI Police School in Lisbon, Portugal. This was attended by Forensic Archaeologists and Crime Scene Analysts from the Netherlands, Sweden, Denmark, Switzerland, Germany and Portugal. Part of the field school involved a simulated exercise as described below:
The Portuguese Police are investigating the disappearances of four persons who went missing at the beginning of 2018. There is information available that the missing persons are buried near a building, in four separate graves. The Portuguese Criminal Police has requested an international team to help them locate these potential graves using different GPR units. Teams will be asked to excavate, map, document and analyze the four graves and to present their preliminary findings to the prosecutor the day after the excavation.
Sensors & Software participated in this exercise, using a Noggin® SmartCart® with a 500 MHz transducer (Figure 1). The Noggin® is a powerful, easy to operate GPR system, that is adaptable to a wide range of applications.
Contrary to what is sometimes depicted on television, GPR cannot show the outline of a body. Instead, operators are typically looking for areas of disturbed soil or anomalies in the subsurface associated with the body.
The search methodology first involved collecting reconnaissance Line Scans to identify areas of disturbed soil. The Noggin® system easily navigated the site despite the long grass and vegetation. Based on the Line Scan findings and obstacles, such as trees and surface tree roots, a grid was set up. The grid covered a distance of 19m from left to right, with the length of each line varying between 1m and 11m. Line spacing was 0.25m apart. The goal of the grid was to generate a series of depth slices to better delineate suspicious areas.
The grid was collected in about 30 minutes and, within seconds, depth slices were ready for viewing on the Noggin® DVL (digital video logger). A depth slice of the entire grid (Figure 3) and a GPR line across one of the graves (Figure 4) illustrate anomalies seen in the GPR data.
After all the teams had completed their survey and presented their results, the excavations began. To simulate a body, plastic dummies had been buried (Figure 5).
As revealed during the excavations, the Noggin® SmartCart® successfully pinpointed the locations of the 4 bodies. Those in attendance were impressed with the capabilities of the Noggin® SmartCart®, including the flexibility to adapt a grid layout to varying field conditions. Rapid generation of depth slices in the field is an asset to police agencies who need to work fast and make important decisions in the field. Data collected with the Noggin® was easily imported into the EKKO_Project® software, where reports were created to present their findings.
Sensors & Software’s line of GPR products allow Forensics & law enforcement agencies to locate evidence in real time and direct their excavation efforts to suspect areas, rather than guessing where to excavate – saving time and increasing the probability of finding important evidence.
