Search Strategy and Planning

The desk-based assessment (DBA) is the intelligence foundation of a forensic search. Done well, it compresses weeks of field time into days by ruling out large tracts of ground before a single person walks them. Done poorly, it leaves the field team to rediscover by trial and error what documents could have resolved in advance.

The DBA draws on a wide range of sources. Historical maps: particularly Ordnance Survey sheets in the UK, USGS quadrangles in the United States, or cadastral records in other jurisdictions: establish land use and ownership at the relevant time. A field that was forested in 1995 but is now open pasture tells a very different story from one that has been farmland continuously for a century. Changes in land use matter because digging disturbs the land record, and later change can conceal or expose that disturbance.

• Aerial photographs: multi-temporal coverage from national archives, Google Earth Pro's historical layers, and specialist suppliers can show soil-disturbance crop marks or vegetation anomalies invisible at ground level.
• Witness accounts: family members, informants, and former associates often provide directional intelligence ("near the old barn", "off the B-road north of the village") that, cross-referenced with maps, defines a manageable search polygon.
• Geological and soil survey data: British Geological Survey, USDA Web Soil Survey, and equivalent national datasets indicate soil type, drainage, and depth to bedrock: all factors that affect both the practicality of digging and the preservation of remains.
• Offender profiling and geographic intelligence: travel times from last known contact location, fuel receipts, ANPR data, and mobile phone cell-site analysis can triangulate probable deposit zones.

The output of the DBA is a defined search area with sub-zones ranked by probability, a list of testable hypotheses, and an initial method selection rationale. This document goes into the search file and may later be scrutinised by a defence expert asking whether the investigation looked in the right places.

No single global standard governs forensic search methodology, but several organisations have published frameworks detailed enough to serve as practical baselines. Understanding them matters not just for field work but because expert witnesses are routinely asked whether a search met a recognised standard.

The ICMP's approach, developed largely through work in the former Yugoslavia during the late 1990s and 2000s, is notable for treating the search as part of a continuous chain that ends with identification, not just with recovery. Every decision taken in the field: where to sink a test pit, which anomaly to investigate first, how to mark a find: is recorded against an anticipated DNA-matching workflow downstream. This cradle-to-identification philosophy is the gold standard for mass-casualty events and is increasingly adopted in single-body cases.

The fundamental choice in any search is between going where the evidence points and covering the ground without prejudice. Both are legitimate strategies. Neither is universally superior. The choice depends on the quality of the available intelligence, the size of the search area, and the legal context.

In a criminal investigation where a witness places the burial within a 200-metre radius of a specific landmark, a hypothesis-led approach is efficient and logical. The team surveys the most probable 10% of the area first, and if that returns a positive result the case is closed quickly. If it returns a null result, the probability map is revised and the next-most-probable zone is tested.

Systematic-grid approaches are used when the area of uncertainty is large, when no credible intelligence exists, or when a court or coroner requires proof that the entire defined area was covered. The ICMP's recovery work at Srebrenica-related sites combined both: intelligence from satellite imagery and survivor testimony drove the initial hypothesis, but secondary-grave locations required systematic coverage of large areas of forest and field.

In England and Wales, any search with forensic implications in a serious crime investigation is coordinated by a Police Search Advisor. The POLSA qualification involves specialist training in search planning, evidence recovery, and legal accountability. Their primary product is the search policy, a written document that records why each method was selected, what areas were searched, what was found, and every deviation from the original plan.

1. Scoping and briefing
   POLSA reviews available intelligence with the senior investigating officer, defines the search area, sets objectives, and briefs the team on the hypothesis being tested and the methods to be used.
2. Method selection and resource allocation
   Based on soil type, terrain, probable depth, and time elapsed since burial, POLSA selects methods: manual probing, canine teams, geophysical survey, or a staged combination. Resources: specialist archaeologists, forensic geophysicists, canine units: are requested and logged.
3. Field execution and tasking log
   Every instruction to a search team, every anomaly investigated, every area cleared, and every find is logged in real time. The tasking log is a contemporaneous record and is admissible as evidence. Alterations must be marked as such; it cannot be rewritten after the fact.
4. Debriefing and review
   At the end of each search day or phase, POLSA debriefs the team, reviews the log, updates the probability map if warranted, and revises the plan for the next phase. If the search is terminated without a positive result, the policy document records the basis for that decision.

Outside the UK, equivalent coordination functions exist under different titles. The US has the FBI's Evidence Response Team leader; international operations use the ICMP site commander or UN-appointed forensic lead. The titles differ; the accountability principle is the same: one person owns the plan and signs the record.

A probability map is a structured spatial representation of the team's current knowledge about deposit likelihood. It is not a formal statistical model. The simplest version is a polygon sketch on an aerial photograph annotated with high, medium, or low confidence ratings; more sophisticated versions use weighted GIS layers.

The factors that drive probability ratings fall into a few categories. Terrain accessibility at the time of the alleged burial: a steep, heavily vegetated hillside accessible only on foot scores differently from a flat field beside a road. Soil characteristics: loose sandy soil is easier to dig and more likely to yield to a probe than compacted clay or rock. Concealment logic: offenders generally choose locations with visual screening, routes that avoid witnesses, and ground that allows rapid digging: factors that produce predictable spatial patterns for experienced investigators.

The map must be revisited as fieldwork progresses. A null result in a high-probability zone shifts probability to other zones and prompts re-examination of the underlying assumptions. A probability map that never changes during a search is not functioning as a planning tool.

Forensic search documentation serves two audiences: the field team executing the plan and the court that may examine it years later. Good documentation serves both. The tasking log, the search policy, the probability map, and the method-selection rationale collectively form the search archive.

• The search policy states the objectives, the area, the methods selected, and the reasons for each choice. It is written before fieldwork and updated when circumstances change.
• The tasking log records every instruction and outcome in real time. It cannot be retrospectively amended without notation.
• The method record documents equipment used, calibration data, survey parameters, operator names, and environmental conditions for every survey session.
• The anomaly log lists every geophysical or canine alert, the location in grid coordinates, the follow-up action taken, and the outcome.

In the UK, the Crown Prosecution Service's guidance on expert evidence requires that the basis for any expert opinion be disclosed, which means the search archive forms part of the disclosure package. In international tribunal work, the chain of custody for search documentation is as tightly regulated as the chain for physical exhibits.