What this planner works out
This planner divides a rectangular scene into search lanes at a chosen spacing, totals the walking distance, and estimates how long a team would take to cover it.
It is a resourcing tool. Knowing that a search will take an hour rather than ten minutes changes how many people are deployed and whether the light will hold. This is a teaching and planning aid, not a casework tool.
Search plan
Before you plan a search
- Lane spacing depends on what is being looked for. Close spacing for small items such as cartridge cases; wider for larger items or a first pass.
- The speed figure should reflect searching, not walking. A careful line search proceeds far more slowly than normal walking pace.
- The model assumes a clear rectangle. Vegetation, obstacles and terrain all increase the real time considerably.
- Team time assumes everyone searches simultaneously in parallel lanes, which requires enough people to cover the width.
Halving the lane spacing doubles the distance and doubles the time, and roughly doubles the chance of finding a small item. A search plan states its spacing precisely because the spacing determines what the search could reasonably have found — and therefore what a negative result means.
How this calculator works
Lanes, distance, then time:
Lanes = scene width ÷ lane spacing, rounded up
Total distance = lanes × scene length
Team time = total distance ÷ (searchers × speed)Rounding lanes up ensures the full width is covered. The time figure divides the work evenly between searchers, which is the best case — in practice, briefing, marking, photographing and recovering items all add to it substantially.
A line search is only one method. Spiral, zone and strip patterns suit different scenes, and the choice is recorded as part of the search strategy.
Worked example: a 50 by 30 metre scene
Using the default figures — 50 m by 30 m, 1 m lane spacing, 5 searchers at 5 m per minute:
- Lanes: 30
- Total search distance: 1,500 m
- Estimated team time: 60 minutes
An hour of pure searching, before any recovery work. Tighten the spacing to 0.5 m and it becomes two hours; widen it to 2 m and it becomes thirty minutes. That is the whole planning decision in one figure — and it is worth noting that a two metre spacing across grass will not find a cartridge case, so the faster option may not be a search at all.
Common mistakes
- Using walking speed rather than search speed. Careful searching is several times slower.
- Planning spacing without reference to the target item. The two are inseparable.
- Ignoring terrain. Vegetation, slopes and obstacles can double real times.
- Treating the estimate as total scene time. Recovery, packaging and recording are extra.
- Assuming a rectangle. Real scenes rarely are, and the model does not adjust.
Frequently asked questions
How is lane spacing chosen?
By what is being searched for and how thorough the search needs to be. A search for a firearm can use wider lanes than one for a bullet fragment. Where the target is unknown, a tighter spacing is used for the immediate scene and wider for the outer cordon. The chosen spacing is recorded because it defines the search's sensitivity.
What search patterns are used?
Line or strip search, where searchers advance abreast, is the most common for open ground. Grid search repeats the line search at right angles for greater confidence. Spiral search works outward or inward from a focal point. Zone search divides a scene into sectors, which suits buildings. The choice depends on terrain, team size and what is sought.
Does a negative search result mean nothing is there?
No, and this is why spacing is documented. A search establishes that nothing was found at that sensitivity, in those conditions, by that team. Lighting, vegetation, weather and searcher fatigue all affect detection. A negative result is evidence of absence only to the extent the search was capable of finding the item.
How many searchers should be used?
Enough to cover the scene width in parallel where possible, so the team advances as a line. Beyond that, more searchers reduce elapsed time but increase the coordination burden and the risk of contamination. Fatigue matters too — detection rates fall measurably over a long search.
Is what I enter stored?
No. Everything you enter is processed in your browser and is never transmitted or retained. Even so, treat any public website as an unsecured environment and do not enter identifiable case information.
Related tools
References
- GOV.UK — Forensic Science Regulator codes of practice for scene examination
- Health and Safety Executive — safe working outdoors, lone working and site hazards
Sources are checked at publication and can change — how I choose and check references.