Blue Line

The valid role of inferential reasoning in use of force cases

Law enforcement, like any other profession, develops its own body of inferential knowledge — knowledge that is accrued though training and experience. This allows practitioners to make informed assumptions regarding the situation they are in. A recent court case involving an officer-involved shooting highlights why inferential reasoning is important when it comes to justifying use of force.

March 14, 2019  By Sgt. Brad Fawcett

If you are a fire fighter, the colour of smoke matters. To the rest of us, it’s just smoke. Similarly, the location from which the smoke appears to originate (front of the house, basement, back of the house) matters to a firefighter because the colour and apparent origin provide immediate information about the type of fire he or she will probably be combatting. More importantly, the firefighter is not working off a paper checklist but, rather, a mental plan honed by training and experience that will be tweaked as more information is obtained.1

Likewise, an experienced waiter or waitress develops job-specific knowledge that has significant implications for his or her salary. The experienced waiter/waitress quickly learns to read body language that has meaning to him or her with respect to freshening coffee, providing condiments and knowing who is ready to pay. A good waiter or waitress can sometimes appear to read minds and this inferential knowledge may result in the customer leaving a larger tip.2

Some instances of inferential knowledge may not be so dramatic: rain has been forecast, the sky is overcast and, like other rainy days you have experienced, you conclude it is likely going to rain. Based on our experience with rainy days, we are almost always right. The consequence of being wrong when relying on inferential knowledge predicting rain is usually nothing more than embarrassment or inconvenience. In law enforcement, apparently innocuous behaviours, many of which are perceived as non-threatening to others, have meaning for the officers involved and the consequences of being wrong can be significant.

In the book Canadian Police Work: 3rd Edition, Curt Griffiths3 noted that police officers develop “typifications,” or constructs of events based on the officer’s experience and schemas; decisions normally made and the actions normally taken in certain situations. Just as the firefighter learns to identify potential dangers based on the location and colour of smoke, police officers learn to identify potential violence and develop strategies on how to address it.4 These strategies learned through training and experience allow for a rapid assessment and force selection. In their research, Michael D. White and Justin Ready indicated that police typically react to situational cues, such as unpredictability and the characteristics of the area in which the incident takes place.5

On a dark September evening in 2009, Const. David Pompeo and his partner were patrolling in a semi-rural Vancouver Island community when they spotted a vehicle driven by a subject they knew to be a prohibited driver. A short pursuit ensued, followed by a brief encounter with the occupants. The driver exited the vehicle and adjusted his position relative to the officer and repeatedly reached toward a jacket pocket. The officer, believing the driver to be reaching for a weapon, shot him. The investigation that followed resulted in the member being charged with aggravated assault and ultimately being convicted in September 2013.


The conviction was appealed on several grounds, including the original trial judge’s decision to disallow evidence of a use of force expert. The B.C. Court of Appeal ordered a new trial concluding that the judge never came to grips with the critical question — was Pompeo’s belief that lethal force was necessary and objectively reasonable and not the product of fear and stress?6 This question would ultimately be answered with the assistance of a use of force expert.

The matter was re-tried in late 2015 and early 2016 with the officer charged with assault causing bodily harm (s.268(2) CCC). Defence called two use of force experts in the new trial; the prosecution did not call an expert. One of the issues raised was that of inferential knowledge.

An understanding of inferential knowledge was necessary to assist the trier-of-facts in determining culpability. Police officers accrue inferential knowledge by participating in foundational recruit training during which they receive instruction in identifying behaviours associated with violence. Instruction may include, but is not limited to, identifying pre-assault cues, characteristics of armed persons, reaction time, reactionary gap, and the one-plus-one rule. Officers accrue more inferential knowledge during their working careers as they observe assaultive behaviour, behaviours preceding assaults, post-assault behaviours, and experience being assaulted. As with firefighting, it is usually not one behaviour that determines response selection but rather a constellation of behaviours that lead a reasonably trained officer to infer that a subject is preparing or initiating an assault.

One of the issues raised by the prosecution at trial was that of bias in the mind of the officer because of special knowledge he had of the suspect with respect to a past conviction for armed robbery and that knowledge may have caused the officer to misidentify innocent behaviours as threatening ones.

In other words, the officer may have increased his perception of risk because he had knowledge of the driver’s past criminal activities, which he may have been made aware of by police dispatch, various police databases or past dealings with the subject. The prosecution’s theory was this knowledge caused the officer to develop an unreasonable fear not supported by objective facts.

There are important reasons why police dispatchers inform officers of the status of vehicles and registered owners, criminal histories associated with addresses and occupants. There are reasons why there are mobile data terminals in cars, which routinely update police officers with information including criminal histories. The information provided increases situational awareness, allows police officers to make informed tactical decisions and to begin the process of an evidence-based risk assessment.

The behaviour consistency model holds that past performance is a predictor of future performance.7 A person who has demonstrated a willingness and ability to inflict violence on another person can reasonably be perceived as more dangerous than one who has not, hence the critical value of background information when dealing with high-risk encounters for public, officer and subject safety.

The original conviction, had it stood, would have had a significant effect on police training; officers would now have to have concrete evidence of a deadly threat before acting to preserve their lives. Such a position would be contrary to decades of police training, which was supported by reaction time studies8 and centuries of blood lessons.9

Officers could have been placed in a position whereby they would have to wait until a weapon was seen before they were justified in responding. This would leave officers in an indefensible position; they would simply be too far behind the reaction curve to respond to a perceived threat.

Officers, in essence, would have to be hit before they coud hit back, despite years of court decions that supported the position that officers or a member of the public may have to hit back first if he or she reasonably believed they are about to be assaulted. This notion is captured in s. 265 (1) CCC:

A person commits an assault when
(a) without the consent of another person, he applies force intentionally to that other person, directly or indirectly;
(b) he attempts or threatens, by an act or a gesture, to apply force to another person, if he has, or causes that other person to believe on reasonable grounds that he has, present ability to affect his purpose; or
(c) while openly wearing or carrying a weapon or an imitation thereof, he accosts or impedes another person or begs.
(emphasis added)

The self-defence provisions of the criminal code found s. 34 CCC, Defence of Person, support the use of “pre-emptive” force:
34 (1) A person is not guilty of an offence if
(a) they believe on reasonable grounds that force is being used against them or another person or that a threat of force is being made against them or another person;
(b) the act that constitutes the offence is committed for the purpose of defending or protecting themselves or the other person from that use or threat of force; and
(c) the act committed is reasonable in the circumstances
(emphasis added)

S. 34 CCC lists several factors to be considered, which includes, “whether the act committed was in response to a use or threat of force that the person knew was lawful” (emphasis added).

The language and case law, as it has evolved, supports the notion that police officers, or anyone, can use force to prevent an assault they reasonably believe is imminent.

The Defence relied on section 25(3) CCC which prohibits the use of lethal force unless the person believes, on reasonable grounds, that such force is necessary for the preservation of that person or another’s under that person’s protection. Section 25(3) requires that a person using lethal force must have a subjective belief that its use is necessary and that belief is objectively reasonable (R. v. Nasogaluak, [2010] 1 S.C.R. 206, at paragraph 34). The prosecution held that the officer acted unreasonably and acted primarily out of fear. While the officer may have held a subject belief that his life was in danger, the prosecution contended that belief was not supported by objective facts.

At trial the defence presented evidence of the knowledge gained through training and experience that would lead any reasonable officer to infer that he or she was about to be assaulted. Behaviour such as not stopping immediately for a police vehicle with emergency equipment activated, reaching toward pockets, repositioning relative to the officer, lowering into a loaded position, non-compliance with commands and/or staring/glaring are all behaviours that could have an innocent explanation and purpose. However, police officers must interpret them considering their training and experience, and in an aggregate or cumulative sense, taking all the components together and making a reasonable inference from it.

The court did not employ a final frame analysis; it considered the evolution of the incident and how it caused the officer to perceive it in a threatening way. The trial judge noted,

“For Constable Pompeo, the shot fired into Mr. Gillespie was the culmination of a series of acts and events, all of which combined to cause him to believe, at the crucial instant, that his life was at risk and that he was thus justified in using lethal force.” [R. v. Pompeo, (2016), BCPC, page 8, paragraph 20].

Importantly, the judge noted that the fact that the driver was ultimately determined to be unarmed at the moment the officer made his decision to shoot had no bearing on the analysis of reasonableness. The trier-of-facts “… must deal with the case as if the driver did have the ability to produce a weapon as Constable Pompeo honestly believed to be the case” [R. v. Pompeo, (2016), BCPC, page 8, paragraph 20].

Const. Pompeo was acquitted after a six-year ordeal. The trial judge accepted the defence experts’ opinion that police officers are typically reacting to demonstrated behaviours that may have an innocent purpose; however, police officers have no way of knowing that. The officer, therefore, is at a significant disadvantage.

An understanding of pre-assault cues and specific strategies and tactics are intended to equalize, as much as possible, the action-reaction time differential. Inferential knowledge allows for rapid decision-making; however, there is a speedaccuracy trade-off, which may result in the misidentification of behaviours. The evidence presented at trial, and accepted by the court, held that inferential knowledge plays a significant and valid role in determining reasonable use of force by police.   

1. Klein, G. (1998). Sources of Power: How People Make Decisions. Cambridge: MIT Press.
2. Streumer, B. (2007, 01). Inferential and Non-Iinferential Reasoning. Philosophy and Phenomenological Research, pp. 1-29.
3. Griffiths, C. (2013). Canadian Police Work: 3rd Edition. Toronto: Nelson Eductation Ltd.
4. Lee, H. &. (2010). Organizational factors that contribute to police deadly force liability. Journal of Criminal Justice, 193-206.
5. White, M. &. (2007). The TASER as a less-lethal force alternative: Findings on use and effectiveness in a large Metropolitan Police Agency. Police Quarterly, 170-191.
6. Mulgrew, I. (2014, 08 09). Mountie Convicted of Shooting Unarmed Motorist Wins New Trial.
7. Fabrigar, L. (2006). Understanding Knowledge Effects On Attitude-Behavior Consistency: The Role of Relevance, Complexity, and Amount of Knowledge. Journal of Personality and Social Psychology, 556-577.
Byrka, K. (2009). Attitude-behavior consistency: Campbell’s paradigm in environmental and health domains. Eindhoven: Eindhoven University of Technology.
8. Silverman, I. (2010). Simple reaction time: Not what it used to be. The American Journal of Psychology, pp. 39-50.
Teichner, W. H. (1954, 04). Recent Studies of Simple Reaction. Psycholgical Bulletin, pp. 128-149.
Siddle, B. (1995). Sharpening the Warriors Edge: The Psychology & Science of Training. Millstadt: Human Factors Research Group Inc.
9. Remsberg, C. (2008). Blood Lessons: What Cops Learn From Life-or-Death Encounters. Glen Ellyn: Calibre Press.

Author’s note: The views expressed are those of the author and do not reflect those of the Vancouver Police Department or the Justice Institute of British Columbia.

Sgt. Brad Fawcett is a 28-year police veteran and a past contributor to Blue Line. He is a court-qualified expert in use of force, police training, non-firearms prohibited weapons, street weapons and weapons concealed by design.

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