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Searching for Buried Murder Victims

Overview 

Police departments are using GPR frequently to help search for evidence in murder cases. When a person goes missing and foul play is suspected, the victim often buried at an unmarked location. GPRs ability to non-intrusively detect disturbed soil conditions as well as the presence of shallow buried objects makes it an ideal method to aid forensics investigations. Results from police forensics training sites show how GPR is often deployed.

Problem

Police missing person investigations call for the follow up on many leads based on sparse information and often ambiguous eye-witness reports.   Searching for evidence in the case of  buried victims can be extremely challenging. With no visual information available and often extensive areas to search, being able to pinpoint zones of interest quickly is important. Often time-limited search warrants demand rapid deployment of limited resources. Efficient search methods that minimize time and manpower resources are needed.

GPR Solution

Noggin 500 MHz SmartCart configurations are the most commonly selected GPR for buried victim detection. The Noggin 500 MHz system provides the right balance of spatial resolution and exploration depth with a sufficiently large footprint to maximize area coverage. Typical unmarked graves have area dimensions of about 0.5m x 1.5m and are in the top 1.5m. The SmartCart provides a self contained survey platform that is light, rugged and quickly deployed on site.

This case study shows results from a police training exercise where training investigations were conducted on controlled pre-placed targets. Trainees used two modes to search for zones of interest.

The first mode is most effect when quick results are needed and forensics dig teams are immediately available to follow up. Trainees surveyed lines with the Noggin SmartCart identifying zones of interest directly from the display screen. Using the back-up arrow capability of the SmartCart, zones were pinpointed and marked directly on the ground. Depth of target was noted and the survey team moved on, leaving the dig-crew to investigate further.

The second mode uses systematic grid surveying to completely blanket an area. This approach is most effective when there are complex subsurface conditions. Trainees established a regular grid of parallel lines to span an area to investigate. (Several grids may be used if the area is large and irregularly shaped.) Each line was surveyed, following the Noggin SmartCart grid mapping user interface prompts. The data were then transferred to a field computer. Using the PC based  EKKO_Mapper software, the data were rendered as GPR response maps at a range of depths. Zones of interest were identified, marked out and prioritized for following up. While results are less immediate, grids surveys reduce false alarms and improve the probability of significant target detection. The systematic approach and automated data processing delivers  results less dependent on operator skill and experience.

The above grid survey covered an area of 10m  by 10m. Time from start to map creation was less than 45 minutes. All work was done by trainees who had only been introduced to GPR on the day of training.

In both survey modes the GPR data can be recorded and save in digital form. If the GPR is augmented with GPS positioning, the data can be geo-referenced for use with a variety of software mapping tools such as ArcGIS, AutoCad, and Google Earth. This capability can be valuable in cases where data are needed for expert witness discussion at a trial.

Results & Benefits 

The above training study demonstrates the value of GPR for forensics investigation when targets are buried in the ground. Some key benefits are:

• Noggin SmartCart is a compact, portable and rugged GPR for forensic site investigations
• Operation is simple and intuitive
• Users can be effective with only a few hours of training
• Systematic search protocols are available as best practice guides
• Locate and mark provides rapid and immediate zone of interest identification
• Grid mapping simplify data analysis and reduce false alarms

GPR responses can vary greatly depending on the type of target being sought and the host material properties. GPR variability can be challenging to first time GPR users. When learning about GPR, the best practice is to review several similar case studies to develop an understanding of variability. Check for other insightful information on the resources tab to learn more. Use Contact Us or Ask-the-Expert to reach our Application Specialists who can help you tap into Sensors & Software's vast array of technical information.