Using Their Reactions Against Them: Identifying Active Threats Through Behavioral Change

When on foot patrol or in marked cars, your officers are noticeable. Their presence often has a deterrent effect. One method that your officers can use to identify active threats is to look for people’s changes in behavior in reaction to their presence.

You, me, your officers, everyone responds to changes in their environment, especially to perceived threats.  Criminals, terrorists, and active shooters will too. They are likely to consider uniformed officers a threat and they may attempt to avoid notice, they may hide, or they may stop whatever they were doing (illegal or not). We can use this reaction against them.

We all know people react to the presence of police, but it is not just the reaction that matters. Law abiding members of the public may slow down if they see a police car. It is other behaviors they display before, during, and after they react which lead to threat identification. That being said, let’s dive a little deeper into why timing of observations matter and how active threats respond to your officers by further understanding the ‘when’ of threat indicators.

Two “Threatening” Scenarios

Many of us will adjust our behavior in threatening situations. Think about the following two scenarios.

Scenario 1: A young child in elementary school didn’t do their math homework. The teacher starts to ask the class to give their answers. To avoid being called on, the child slouches down at their desk and looks down at the ground, hoping that the teacher won’t notice and call on them. 


Scenario 2: A young woman is walking home late at night. The streets are deserted, and visibility is poor. While walking, she notices someone walking towards her on the same on the same side of the road. She quickly crosses to the other side of the street to put some distance between herself and this other person.

What’s really going on in both of these scenarios? In scenario 1, the child is reacting to the fear of being caught unprepared by the teacher. In scenario 2, the young woman is reacting to the potential threat of the person coming towards them.  They are responding to changes in their environment, changes that could be harmful.

Observing Active Threats: Changes in Behavior

Research in psychology has long described the phenomenon by which individuals change their behavior after becoming aware that someone is observing them. The “Hawthorne Effect”, as it is known, originated from a study of factory workers at the Hawthorne Works facility of the Western Electric Company in the 1920s and 30s. Initial findings from Mayo (1933) suggested that factory workers increased their productivity when factory lights were turned up brightly due to the belief that supervisors were watching; since that time dozens of articles have revisited these investigations to new domains such as healthcare and classroom settings (McCambridge, Witton, & Elbourne, 2014).

But, the Hawthorne Effect also applies to police, security, and military environments. As observers, your officers know that the behavior of an individual will change based on their assessment of perceived threats. Active threat assessment requires a systematic observation of their environment while accounting for context in the locations being observed. Each place has a pattern of consistent behavior or baseline.

Stage of Interaction: Reaction and the ‘When’ of Threat Indicators


Reaction is an important part of active threat assessment. Use of behavioral changes to identify active threats should be combined with systematic observation of the location being observed and an assessment of the roles, objectives, and patterns of consistent behavior of those present. It is not just changes in behavior that matter.

When your officers identify someone reacting to their presence or who could be an active threat, they may decide to act or watch further. Whichever they choose, your officers should continuously observe and look for behavioral changes.

 To help police officers think about changes in behavior over time, we have identified five stages of interaction associated with behavioral observation. These stags are relevant when interacting with any potentially threatening individual and relate to how a subject behaves when they perceive a threat.  

When describing behavior and the stages of interaction, we use the term officer to represent the observer and subject to represent the person being observed.

  1.  Unthreatened: How a subject behaves when an officer is not present, and they do not feel they are under any direct threat from police or any other person in their environment. It is important to note this does NOT mean the subject does not believe they may be a target, only that they do not see a specific threat.  

  2. Present: How a subject behaves when an officer is in the general area, but when they do not believe the officer is observing them in particular. The best way to describe this is how a subject behaves when a patrol car is stopped down the street, but the subject does not not believe they are being watched by the officers in the car.

  3. Watching: How a subject behaves when they believe they are under “surveillance” by an officer.

  4. Initial Contact: How a subject behaves when they are approached and are in the beginning stages of an interdiction with an officer.

  5. Interdiction: How a subject behaves during the verbal and behavioral interplay between an officer and a subject.

A subject’s behavior is likely to change if they feel threatened, when they know they are being watched by law enforcement and during an interaction. This just makes sense.

Take a quick look at this video. You see the subject in the gray coat in Stage 1, when he does not seem to be under direct surveillance by a threat. Then you see him in Stage 3 when he notices he is being watched. He is then approached (Stage 4) and then there is an interdiction (Stage 5). Behaviors displayed by the subject in changes across the encounter and the display of specific threat indicators may cause the subject to perceived as more or less of a threat.

When interacting with people and observing for potential threats, it is essential that your officers assess how people are reacting to their presence. Thinking about what is observed through the lens of these stages of interaction will help your officers plan and conduct a safe and effective interdiction, keeping themselves and others safe.  Want to help your officers become even more proficient at identifying active threat indicators and WHEN to act? Check out our active threat course offerings today!


Mayo, E. (1933). The Human Problems of an Industrial Civilization. New York, NY: Macmillan Co.

McCambridge, J., Witton, J., & Elbourne, D. R. (2014). Systematic review of the Hawthorne effect: New concepts are needed to study research participation effects. Journal of Clinical Epidemiology67(3), 267–277.

Meehan, N. and C. Strange. (2015). Behavioral Indicators of Legal and Illegal Gun Carrying. Memorandum Report - NRL/MN/5508--15-9597. United States Naval Research Laboratory.