Lost Person Behaviour

In predicting lost person behaviour, it is useful to perhaps place them into ‘Subject Categories.’  There has been a lot of work done on this over the years but doesn’t it make sense that a lost child at a fair is going to behave differently that a suicidal adult?

SAR Team members can use this to predict behaviour and increase their likelihood of finding the missing person.  First they need to need to be able to place them into one of the different subject categories and then understand certain behaviour traits the Missing Persons have.  Then they can use that knowledge to predict actions and allocate resources that reflect those predictions.  A lot of these studies have come out of North America but there are also many UK sources.  There are numerous excellent research, books, studies, texts, websites and courses out there on the subject and many notable authorities.

For example, I was in speaking at a SAR conference in the US in 2007 I met a man named Robert Koester.  I enjoyed speaking with him as we seemed to share the many of the same philosophies on some SAR things.  I found out about his book called “Lost Person Behavior” which reports on 41 subject categories from the International Search & Rescue Incident Database (ISRID) which contains over 50,000 SAR incidents. 

This data has been collected from Australia, Canada, New Zealand, South Africa, Switzerland, United Kingdom, and the USA). He states that whilst additional subject categories exist, these are the ones with sufficient data to currently report.  Robert J. Koester’s work and studies on such matters is highly regarded and his materials are worth the read.

I would also like to give credit to William (Bill) Syrotuck who probably did the earliest key work.  But Mr Koester has really built upon his work in a really big way with his detailed analysis of so many statistics from around the world.  For a better look at the history and full credits to the many sources and people expert and known in this field, I recommend you read Mr Koester’s book on Lost Person Behavior.
Naturally not all subject categories listed in North America are common to the United Kingdom – for example snowboarders, alpine skiers and hunters are not so common.

But human nature being what it is and the fact that SAR teams can use this material out there to help them, means that it is very worth looking at.  I am also aware of other studies and statistics such as the ones by Pete Roberts and Dave Perkins in Northumbria. (Dave Perkins told me of their work on the website: www.isaralliance.com  Please check it out.) 

I have summarised these categories on the table on the next page for your review.

Subject Profiles

Robert Keoter’s 41 subject profiles from his studies in his book Lost Person Behavior.








Child 1-3

Child 4-6

Child 7-9

Child 10-12

Child/Youth 13-15






Horseback Rider


Mental Illness


Mental Retardation (Intellectual disability)

Mountain Biker

Other (Base Jumper)

Other (Extreme Sports)

Other (Motorcycle)






Substance Abuse

Urban Entrapment

Vehicle (Missing vehicle)

Vehicle (4WD)

Vehicle (Abandoned)

Water (Powered boat)

Water (Non-powered boat)

Water (person in flatwater)

Water (PIW - current)

Water (PIW - flood stage)


A summary of some pertinent headings follows. I recommend looking at Robert’s book for a more detailed source of information on the subject.

UK Information
The UK Missing Person behaviour Study Report of 2005 lists a few different subjects’ categories which were probably considered more indigenous to the British Isles.  These were connected with Messers Perkins and Roberts of The Centre of Search Research (CSR) and I have listed them below.  For a more detailed look contact the CSR.

Subject Category of The Missing Person(s).
Alzheimer’s sufferer
A person diagnosed as suffering from dementia of Alzheimer’s type

Child (1 to 6 yr.)
Child’s chronological age only

Child (7 to 12 yr.)
Child’s chronological age only
Youth (13 to 16 yr.)
Child’s chronological age only
On or off route, accessing into or out of the climb.
Dementia sufferer
Developmental problems
A person diagnosed as suffering from dementia other than Dementia of Alzheimer’s type
Individuals whose mental age is significantly different from their chronological age anyone where there is evidence that they have deliberately disappeared as a result of clinical depression or intention to harm themselves.

Fell runner
Either as a competitor in an event, training or recreation, including orienteering.

Hiker / walker
Any form of recreational walker, of whatever length, involving persons 17 yr. +
Any other use of the outdoors not included in the earlier categories – photographers, mushroom pickers, birdwatchers etc.  Anything not included in other categories, for example missing swimmers, missing from road traffic accidents and crime related incidents.
Mountain Biker
Where the bike was the main means of transport, on or off-road.
Organised Party
A party with a recognised leader or purpose.

Psychological illness
Any person with significant mental impairment other than those contained in the categories Alzheimer’s sufferers, general dementia, developmental problems.  Psychological illness persons identified by a medical practitioner as suffering from a mental illness; they may be undergoing treatment either at home or appropriate place
If so equipped, including the walk in and out.
Anyone who can be described as having significant mental impairment e.g. mentally handicapped, dementia sufferers(senile or Alzheimer’s), sufferers of  psychoses.

Search Planning

Most front line operators probably do not get too involved in the ‘Search Planning’ and ‘Search Management’ however it is important that you know certain terms and operational definitions. 

These more specifically refer to open area land type searches rather than USAR terms or maritime or military   Many USAR terms will be covered in that section later in the book.  Many of these terms are used in mathematical equations used to determine the location of the missing person.  For the Search Manager this is a rather important function. 

The average operational search technician should be aware of this but will not likely get too involved in the planning process.  I certainly doubt they will use all the calculations in the field.  Here are some of the well used and lesser used terms and definitions, as well as a few of the used in search planning calculations.  It is useful to know but I am not suggesting you will use this all the time or even much as a tactical or operational SAR Technician.

Area of Possibility (AoP)

The area that the Missing Person is thought to maybe be.

Initial Planning Point (IPP)

The planning point that usually starts the search in the first place.  The plan is initially created there. The IPP may be the original PLS or LKP.  It is also sometime the place where you expect the subject to return to, like their car or campsite.

Last Known Point / Position / Place (LKP)

LKP is the last spot at which we can definitely establish the victim’s presence by things like: radio reports, telephone calls, trail logs, physical information like the victims car or personal equipment located.


The study number that represents 50% of cases. Half the numbers are less and half the numbers are more.

Point Last Seen (PLS)

PLS is the spot anyone actually saw (radar skin paint counts) the missing person/aircraft.  PLS is usually established by witnesses.

Probability of Area (POA)

The likelihood or probability that the subject is located in a specific area; expressed as a percentage (e.g. 50% ) or decimal number (e.g. .50 ).  (POA is probably equal to the term, “Probability of containment” (POC) in the maritime and water rescue world. Also known as the likelihood you are searching in right place.

Probability Density  

The POA of a specific area or segment, divided by the size of the physical area and expressed as a ratio.  High Pden segments will normally receive higher priority.  Calculation below:

Pden = POA



Probability of Detection (PoD)

The likelihood of probability of finding clues (assuming that clues are available to be found ), given the nature of the search and the type of resources employed; expressed as a percentage ( e.g. 50% ) or decimal number (e.g. .50). Also known as the likelihood you will detect the person if you are in the right place.  (Like many of these, the POD is probably more useful for search planners than for search technicians.)  The only time you have 100% POD is if you actually find the target!

Probability of Success (POS)

Probability of Success (POS):  The probability of finding the subject in a specific place or area, given the type of search tactic employed.  POS measures search effectiveness and is derived from the formula  POS = POA x POD.

These are not even nearly all, of the acronyms and maths!

Science and Maths are important

SAR Team members should know of the basic equations and understanding of maths for searches.  There are also scientific or mathematics that can be used to assist searches.  This includes the maths of motion and kinetics in science like when someone gets thrown by water or a vehicle to see where they may have landed.

Also calculating a Theoretical Search Area and why time is so important in mobilising trained searchers to the area.  Any delay in calling or deploying etc., may exponentially increase the search area.  An equation like

Theoretical Search Area:  Π=πr2 where pi is 3.14 or 22/7

Example: If they are walking at 2 mph after one hour the search area is 3.14 x (2 x 2) or almost 13 square miles.

But, if they are walking at 2 mph but the time lapse is 2 hours then the theoretical search area quadruples in just double the time to almost 50 square miles, etc. making this a very urgent matter!

It can get quite involved and very impressive mathematically.. 

For example in one text headed “Compatibility of Land SAR Procedures with Search Theory” by Messers Cooper, Frost and Robe as it talks about the U.S. Coast Guard’s Computer Assisted Search Planning (CASP) software which uses a very simple algorithm to adjust POA after searches have been conducted. This method was published to the land search community by Cooper (2000 p21) in the following form:

POAs,n = POAs,n-1 ×(1 – PODs,n)

POAs,n  is the adjusted POA value in segment s (based on the initial POA value established in consensus c for region or segment s) after all searches (hereafter, c shall be presumed to be 1 unless otherwise specified). This value accounts for all searching done to date in segment s.

POAs,n-1 is the adjusted POA value in segment s (based on the initial POA value established in consensus c for segment s) for the specific search just before n (e.g., n minus1). This value accounts for all searching done in segment s prior to search n.

PODs,n is the probability of detection for search n in segment s. This value is not a cumulative value and indicates the POD for search n only.

So from this equation you can see an example of the extensive maths and calculations being used by some Search Planners and Computer Programmes to help predict the whereabouts of the missing and lost.  The paper also goes on to state that the final equation for calculating the cumulative segment Probability of Detection:

PODcums =1((1PODs,1,c )×(1PODs,2,c )×...×(1PODs,n,c ))

Cumulative Segment POD (PODcums) - After the same segment is searched multiple times, the chances of having detected the search object, if it was present in the segment the whole time, are increased as compared to having searched the segment only once. This increasing probability of detecting a search object after multiple searches in the same segment is called cumulative segment POD.