Locating Bodies with GPR
Written by Troy De Souza & Fernando Constantino   

THERE ARE MANY APPLICATIONS for ground-penetrating radar (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 that 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 archeologists 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 Criminal Police are investigating the disappearances of four persons who went missing 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.

Manufacturer Sensors & Software participated in this exercise, using a Noggin SmartCart with a 500 MHz transducer (Figure 1).


Figure 1. Surveying with the Noggin 500 SmartCart GPR.

Contrary to what is sometimes depicted on television, GPR cannot actually 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. Based on the line-scan findings and obstacles, such as trees and surface tree roots, a grid was setup. The grid covered a distance of 19 m from left to right, with the length of each line varying between 1 m and 11 m. Line spacing was 0.25 m apart (Figure 2). The goal of the grid was to generate a series of depth slices to better delineate suspicious areas.


Figure 2. Collected lines overlaid on an aerial photo.

The grid was collected in about 30 minutes and depth slices were ready for viewing on screen. 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.


Figure 3. Slice at 20-25cm depth.


Figure 4. Cross-section line crossing grave number four.

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).


Figure 5. Plastic dummy buried.

As revealed during the excavations, the GPR successfully pinpointed the locations of the four bodies. 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 was easily imported into the software, where reports were created to present their findings.

Using GPR in the field allows law enforcement agencies to locate evidence in real-time and direct their excavation efforts to suspect areas, rather than guessing where to excavate. This saves time and increases the probability of finding important evidence.


About the Authors

Troy De Souza is training manager at Sensors & Software Inc. and has been with the company for 18 years. In addition to delivering training courses to customers worldwide, De Souza has been a guest lecturer for courses in engineering and non-destructive testing at various universities. He holds a B.Sc (Hon) degree in physics from York University in Toronto, Canada.
Fernando Constantino is an applications specialist with Sensors & Software. With a background in geophysics, Constantino looks after sales and technical customer support for users in Europe. He has a degree in geological engineering from Aveiro University in Portugal.


This article appared in the Fall 2018 issue of Evidence Technology Magazine.
Click here to read the full issue.

 
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