Missing Persons Investigation

When an individual goes missing it is important that a thorough investigation be conducted. A missing persons investigation should focus on human sources and a review of information such as bank records, social media and diary entries.


It is also essential that a prevention interview be carried out. This should be recorded and shared with all officers who deal with the case.

Preliminary Investigation

If a person disappears, law enforcement authorities will launch a preliminary investigation. This is the first step in sizing up the case and determining what investigative tasks need to be done, such as interviewing witnesses and gathering evidence.

It is crucial that a missing persons case be reported as soon as possible. Police agencies often stress that a missing person should be declared within the first 48 hours of absence, as this allows investigators to contact eyewitnesses while they have fresh memories of the suspect’s appearance.

This initial step is largely an information gathering exercise, with the police interviewing close friends and family members. It is helpful if you are able to provide information such as current photographs, physical descriptions, a list of medications the person may be taking and any nicknames they might use. Ask the police if they have access to the National Missing and Unidentified Persons System, which allows you, family members, police and medical examiners to enter information about the case into one central database that is accessible to all involved.

Some disappearances are purposeful and planned, with the person fleeing a legal situation such as an outstanding child support or alimony debt or hiding from dangerous people, such as gang members or drug cartels. In such cases, charities such as the National Center for Missing & Exploited Children or Polly Klass Foundation may be able to assist.


The process of interpreting sightings is often highly uncertain and can involve interpretation biases (i.e., false rejections of valid observations, or acceptance of incorrect ones). The resulting decisions can have conservation implications and impact the efficiency with which conservation actions are implemented.

For example, a failure to adequately consider ambiguous sightings may result in over-optimistic predictions of extinction dates, or even the use of wrong conservation interventions (Roberts and Jaric 2016). On the other hand, overly relying on unreliable sightings may lead to inefficient conservation actions that do not sufficiently target scarce species (Boakes et al. 2015).

Existing methods for handling mixed-certainty sightings typically involve consultation with experts, or the use of a classification scoring system to assign “plausibility ratings” to individual observations based on their type (e.g., McKelvey et al. 2008).

However, the reliability of such assessments is difficult to establish due to the uncertainty inherent in the observation process. A new approach aims to reduce such uncertainty by randomly resampling with replacement from a sample sighting record, using each observation’s reliability as a surrogate probability for inclusion or rejection. The resampled record is then used as input to an EDE model. For Lazarus and definite species, this approach results in improved predictions of persistence or extinction over and above the S93 and OLE models in their original form (Table 1).

Identifying the Person

The identification process is a key step to clarify the fate and whereabouts of an individual who disappeared. It involves collecting, collating and analysing information from various sources: personal data (e.g. physical and dental profiles, family history, lifestyle habits, associations and relationships), communication data such as telephone and satellite call records, photographs (close-ups of the face and upper body tend to work better than wider shots), cyber-communication data such as social media posts, audio and video graphic material, street, aerial or satellite photography of the place of disappearance and its surroundings, etc.

It is important to note that missing persons are defined by their absence from the accustomed network of social and personal relationships, in a context where the person has not performed or will not perform expected tasks (Payne, 1995). Disappearances have been used in all regions and conflict contexts, and the practice has been carried out by both states and non-state actors, with particular focus on targeted groups such as human rights defenders, relatives of those who have already disappeared, or lawyers working on cases involving these individuals.

An important point is that, irrespective of the type of investigation (humanitarian or criminal), each person who disappears should be assigned a unique file number (UFN). This facilitates centralized and unified management, effective exchange of information and professional management of physical evidence.

Identifying the Cause of the Disappearance

The identification of disappeared persons is a complex and challenging task. It involves reconstructing in retrospect a person’s journey to clarify their fate and whereabouts.

It starts with elaborating a list of missing and unidentified individuals, as exhaustive as possible, centralized and unified among the institutions or organizations involved in the process. This list should also be dynamically reassessed along the analytical process (e.g., in the context of mass graves of commingled remains).

The information gathered during this phase should include physical and medical profiles, family data, lifestyle habits (work, study, hobbies), relationships with other persons, nicknames or political aliases, social media or cyber communication links, etc. It should also cover the circumstances surrounding their disappearance and whereabouts (e.g., criminal or non-criminal events that may have affected their situation, armed conflict or natural disaster, trafficking of people in or out of the country, etc.).

Working on these cases can be extremely distressing and frustrating. It can involve searching in mass graves or seeing the remains of people who have been subjected to horrific treatment. For that reason, it is important to have a support network in place that includes colleagues and a good therapist to help alleviate the stress of this work. All staff should be informed of the psychological impacts of working on these types of investigations.