Geoforensics and Information Management for crime Investigation (GIMI)
Challenges in forensic investigations
A main aim of the GIMI network is to widen the application of geophysical techniques to crime scene investigation. Whilst such technology can in many instances increase areas of search, save on manpower and avoid the disturbance of crime scenes, its usefulness is currently limited because of the particular environmental conditions at some sites, such as the soil type and mositure content.
Many such conditions have a geographical basis, which currently excludes many regional police forces from utilising these new techniques.
The main problems relating to the use of geophysical methods at crime scenes are:
- That the physical properties of buried human remains are often difficult to contrast with some environments they may be buried in. More research is needed in this area.
- Indirect detection is assisted when other artefacts associated with the victim are present.
There are a number of reasons for this. For instance, the physical properties that affect radar waves as they travel through a medium are electrical conductivity and magnetic permeability. For soils with a high conductive property (e.g. containing salt or water), and for soils with minerals that have high conductivity, energy will attenuate at a much shallower depth, resulting in a poor reception.
In wet unfavourable conditions, particularly in soils that contain certain clay-rich minerals, the maximum depth of radar penetration in the ground can be less than a metre. Media that contain magnetite minerals, iron oxide cement or iron-rich soils can all have a high magnetic permeability. The higher the magnetic permeability, the more electromagnetic energy will be attenuated during its transmission, resulting in insufficient clarity.
Some of the important factors that must be considered are:
- electrical properties of the ground at the site
- depth of radar/electrical/electromagnetic transmission
- size and dimensions of the features that must be resolved
- site access
- presence of possible external interference within the frequency spectrum of use
Currently, radiometric application is not appropriate for many highly organic and wet site conditions, i.e. areas of peat and soils with high moisture content.
Consequently, other techniques, such as Ultra-wide band (UWB) radar, low frequency electromagnetic devices (1 to 25 kHz) have also been considered (Scott and Hunter, 2004), although with limited success. They concluded that resistivity mapping may be more appropriate for locating and delineating large features such as mass graves.
One of the major aims of the GIMI network is to address issues such as these and to find ways that either improve the technologies being currently used, or finding other, novel solutions to these problems.