The European GPR Association Policy on Forensic Investigations
1. The Nature of Forensic Investigations
Although forensic investigations using GPR are relatively rare, they are generally critical in
nature being primarily to enable the recovery of buried human remains, illegal items such as
weapons, or other material associated with the commission of one or more crimes. It is
extremely important that any GPR operator involved in this type of GPR investigation has
the requisite experience and understanding of the equipment to be used, the nature of
targets to be detected and the ancillary procedures to be observed during and after data
collection. Forensic surveys are not suitable investigations for novice GPR users (see also
Section 7 below).
There is a second category of forensic investigation in which the GPR operator may be
required to make a court appearance as a witness, based on his/her investigations. This is
where GPR is used to verify the completion of a contract as part of a dispute. Typically but
not exclusively these are structural investigations.
2. Survey Assessments
2.1 In advance of the forensic investigation, the GPR operator should carry out a site
assessment which should include the collection of the following information.
 Definition of the survey area(s) [to include the boundaries of the search
area, and the nature of the site surface(es)].
 Where applicable, any available information on the type of target to be
detected, its likely size and shape (remembering, for example, that human
remains are not always buried in a uniform manner) and potential depth.
 Where applicable, any available information on the site characterisation that
is sought (for example, as part of an elimination exercise).
 In the case of ground, open or man-made, an indication of the type of soil
and the level of groundwater.
 In the case of built structures, the building material and any other known
characteristics.
 The time elapsed since burial of the target.
 Potential surface obstacles which may impede deployment of a radar.
2.2 Based on the information gathered in 2.1, the forensic investigator should carry out an
assessment of whether or not a GPR survey is likely to be successful or not. This
assessment should include consideration of whether or not an alternative geophysical or
other technique might be more cost effective, accurate or practical. This assessment must
be recorded so that any GPR survey carried out has an explicit planning record. Although
police forces are usually extremely diligent in providing appropriate information and
background material, it is the responsibility of the forensic investigator to ensure that
he/she has all the relevant information available in order to make this judgement.
2.3 For cases where the probability of a forensic survey being successful is low, the GPR
investigator must bring this to the attention of the Police Search Officer (PSO). In view of
the critical nature of most forensic GPR searches, it is acceptable for such a survey to go
ahead but it is important that the senior Police Search Officer is given the opportunity to
discuss the potential adverse factors and the understanding of what might prevent the
search from being successful or render the results ambiguous. In all cases the GPR
specialist should offer advice based on his/her site assessment and accept the informed
decision of the PSO.
3. Survey Strategies
3.1 Once the decision has been made to deploy GPR, a survey strategy should be drawn up.
The GPR survey strategy should be defined in advance of the survey and should be recorded
in case it is necessary to refer to it at a later date.
3.2 The survey strategy should be based on the survey assessment and should ensure that the
probability of locating the target is as high as can be, given the constraints of the
surrounding environment.
3.3 The survey strategy should also be designed to be economically worthwhile. It would not
be appropriate for a GPR searcher to waste time and resources unnecessarily.
3.4 It may be necessary to deploy a stratified sampling strategy in order to make the best use of
available resources. Sampling strategies must be structured so as to maximise the
possibility of uncovering the target sought. In order to develop a suitable strategy, the
forensic investigator should start from the overall direction and guidance set by the Senior
PSO. The sampling strategy should fit into the Senior PSO’s search strategy and be
adequately explained in terms of the search priorities. The strategy and any explanation(s)
should be recorded.
3.5 The sampling strategy should be discussed with & approved by the Senior PSO or an
equivalent.
3.6 The survey strategy should also comply with the minimum specifications laid down in the
English Heritage guidelines “Geophysical Survey in Archaeological Field Evaluation”, issued
2008. It is the primary responsibility of the forensic investigator to ensure that appropriate
search parameters and equipment are used. He/she is expected to use his/her professional
judgement. Deviation from the EH guidelines is acceptable when the search circumstances
are appropriate. This decision and the reasons for it should be recorded.
4. Survey Results
4.1 In the case of positive results i.e. the recovery of buried human remains or illegal weapons
there is often no further requirement for the GPR operator to contribute to the
investigation since the results of the GPR survey will allow other forensic experts to gather
relevant information. In these circumstances it is likely that the GPR operator will not be
required to attend court as a witness.
4.2 Even if the GPR operator is not required to attend court, all search records should be
retained for a minimum of X years.
4.3 In the case of negative results, particularly if the aim of the search was to eliminate one or
more locations from further investigation, there is a higher probability of the GPR searcher
being required as a witness. It is therefore important that the GPR searcher keeps a proper
record of all work done, any areas selected for trial holes and the results of all ancillary
investigation.
4.4 Since it is not possible to tell in advance of a GPR investigation what the outcome will be, it
is necessary to prepare appropriate records of planning, execution and results for all
forensic GPR surveys.
4.5 All records for GPR forensic surveys must be kept for a long as any relevant police or other
enquiry continues and for at least 1 year thereafter.
4.6 All members of the Association taking part in forensic searches will respect the
requirements of their fellow forensic specialists including not damaging potential sources of
information during the investigation. This can be done either by direct liaison or through
PSOs.
5. Reporting
5.1 It is normal police practice to carry out a team debriefing after a search has been
completed. The GPR forensic searcher should contribute to this discussion but only in
connection with his/her part in the search.
5.2 If the search has been successful, the GPR searcher should briefly describe the rationale
behind the survey strategy and its relevance to the successful outcome.
5.3 If the search has been unsuccessful or has been used to eliminate a site from further
investigation, it is the responsibility of the GPR searcher to briefly describe the rationale
behind the survey strategy and to explain why the forensic search was adequate for the
required purpose and what conclusions can reasonably be drawn from the work done.
5.4 If the search has been unsuccessful or is to be used to eliminate a site from further
investigation but the GPR searcher considers that further work is necessary, it is the
responsibility of the GPR forensic expert to bring this to the attention of the PSO.
5.5 In exceptional circumstances, GPR operators may be advised that their findings are not
going to be followed up by the police, in whole or in part. In these unusual circumstances
the police officer(s) responsible for this decision will normally provide a reason. Although it
is not normally the duty of the GPR forensic searcher to challenge this decision, GPR
forensic investigators should be aware of the possibility that such a decision might be
suspect and contrary to the cause of justice. If so, this decision could and should be
challenged either through a higher ranking police official or through the agency of another
force. The GPR forensic searcher should also bring the matter, in confidence, to the
attention of the current EuroGPR committee or the forensics group.
5.6 Where requested to do so, the GPR forensic searcher should produce a report on the work
done. This report should include the survey assessment, the survey strategy, the survey
work carried out and all relevant findings. Although a report is not mandatory if it is not
required by the PSO, the production of a report represents best practice.
6. The Impact of Research
6.1 There are a number of GPR research projects in progress internationally, aimed at learning
more about the processes of decomposition and the effectiveness of geophysical methods
of discovery.
6.2 All GPR forensic investigators should be aware of papers published on the results of these
research projects. Relevant papers are included in the technical papers from the biennial
international GPR conference, hosted by EuroGPR on its website. The Geological Society
also holds a biennial 1 day conference in London at which research results and case studies
are presented.
6.3 The Association encourages participation in research projects by all members with forensic
experience. Not all research projects start from the basis of practical experience and the
input of members with practical forensic experience is extremely valuable.
7. Professional Affiliation & Training
7.1 All GPR professionals taking part in forensic investigations should subscribe to an
appropriate Code of Conduct through professional affiliation to the European GPR
Association, the Geological Society of London, the Institute for Archaeologists or a similar
professional organisation. Individuals are expected to take very seriously their responsibility
to maintain the highest standards of integrity, responsibility and professional knowledge,
and to restrict their practice and advice to matters within their areas of experience and
expertise.
7.2 It is expected that GPR operators taking part in forensic investigations should have previous
forensic experience. If the Association member does not have relevant experience, they
should either not undertake the work or arrange to do so under the supervision of an
appropriately qualified and experienced expert.
7.3 All GPR forensic searchers should seek the appropriate accreditation from the Forensic
Society, currently under development. The Association is working with the Forensic Society
to develop appropriate training and peer reviewed accreditation.
7.4 Any GPR investigator who may require to make a court appearance as an expert witness
should make sure that they have appropriate training, including on court procedure. The
UK Forensic Society can provide suitable training.
Date submitted to the Committee for approval: 27th April 2012
Date circulated to Members with Forensic experience: 27th April 2012
Date Version 1 revised: 25th May 2012
Date approved: 25th May 2012