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A Survey of the Research on Human Factors Related to Lethal Force

Encounters: Implications for Law Enforcement

Training, Tactics, and Testimony


Interviewing and Incident Recall


Striving for perfection in the total recall of an officer after an incident, particularly in the areas of perceptual processing and memories of performance, may be a worthy ideal; however, as a practical goal, it is not achievable. Error can never be entirely eliminated. The goal of the interview is to find the truth; it is as simple and as complex as that. Officers, investigators, and the police executives who evaluate performance must have a basic understanding of the critical factors that affect both perception and performance under stress. Efforts to maximize opportunities for the integration of the most reliable information (e.g., event narration, viewing videotapes of the incident, doing a walk through of the scene, discussing the incident with other officers on scene) while at the same time reducing contamination from outside sources (e.g., the media, uninvolved peers, etc.) can enhance accurate recall (Loftus, 1979; Loftus & Green, 1980; Loftus et al., 1978; Marshall, 1978). However, these same techniques, in addition to guided imagery, context reinstatement, mild social pressure, and encouraging repeated attempts to recover the memory, are also the ones most at risk of eliciting a false memory (Loftus, 2002). Ultimately, the risk of contamination and confabulation, deliberate or not, must be weighed against the benefits of improved recall.


While there are officers who, for any number of reasons, may intentionally fabricate the facts of an incident, skilled interviewing by an investigator familiar with the research related to perception and performance, combined with a solid forensic assessment of the scene, should provide ample opportunity to differentiate mistakes of fact from conscious attempts at manipulation of the evidence (Fisher & Geiselman, 1992). Memory for stressful events must be understood in terms of complex interactions between the types of event (emotional versus neutral), the type of detail (central versus peripheral), time of interview (immediate versus delayed), and retrieval conditions.


Interventions, including removing the officer from the scene to a lower stress environment, recommending exercise to burn off excess adrenaline, providing the opportunity for a normal sleep cycle, and allowing for the passage of time prior to participation in a detailed interview to mitigate the need for the officer to “fill in the blanks,” can minimize the risk of confabulation. The resulting personal narrative that is critical to traumatic incident recall, while not perfect, will likely be more reflective of the true facts of the incident. Admonitions to the officer to avoid outside influences, including participation in discussions of incident details with family and friends or colleagues, as well as to avoid viewing media reports prior to the initial interview, should also occur. If a detailed interview must be immediately conducted following a critical incident, a follow-up interview should occur the next day with the understanding that additional and potentially conflicting information may result as a normal part of the memory consolidation process and cannot be automatically assumed to be indicative of lying.


Lessons Learned


• Error can never be eliminated entirely.


• Memory enhancing techniques work to maximize accurate recall but also increase the risk of eliciting false memories.


• Discrepanciesshouldnotautomaticallybeassumedtobetheresultofconscious deception but, rather, a function of the memory consolidation process.


• Utilization of state-of-the-art interviewing techniques is critical to maximizing accurate incident recall while minimizing the effects of contamination and confabulation.


• Following involvement in a traumatic incident, affected officers should be removed to a low-stress environment to reduce the negative impact of heightened physiological and emotional arousal.


• The officer should then be provided with the opportunity to give a basic, detailed incident narration with specific questioning to occur at a later time. Admonitions to avoid contamination from outside information sources relative to the incident should be given and the officer should be sent home to sleep.


Memory consolidation and the development of a personal narrative will further enhance recall. The officer should then be re-interviewed the next day, first with an opportunity to provide additional, unsolicited information followed by utilization of accepted memory enhancing interviewing techniques, including context reinstatement, guided imagery, and specific queries as well as an opportunity to participate in a walk-through. A subsequent interview should then be conducted within a few days. This protocol maximizes the quantity and quality of the information obtained. Some variations in reported information will naturally occur as a side effect of the memory consolidation process.




An understanding of the various factors that contribute to errors in perception, mistakes of fact, performance deficits, and inaccurate incident recall is essential to the modern-day law enforcement executive and should serve to guide a department in effectively training and fairly evaluating the actions of its personnel. A large body of research reflects how common these phenomena really are. An understanding of the science of human factors in force encounters needs to become an integral part of the investigation. Expectations that officers can defy the laws of science and exceed the limits of human performance are unrealistic. Therefore, law enforcement agencies and the public must come to understand that it is unrealistic to expect infallible judgment, flawless performance, and comprehensive recall from every officer in every circumstance wherein the officer is tasked with making split-second decisions involving life or death.


A given organization must weigh the relative risk and liability that the organization wishes to assume for, for example, failing to shoot an armed combatant, potentially resulting in the death of an officer, versus accidentally shooting an unarmed suspect. Likewise, the benefits of enhanced incident recall must be weighed against the risk of intentional falsification of evidence by involved personnel. These should be conscious decisions made in line with an organization’s mission and core values, and clearly articulated to all its constituents. Life and death encounters involve difficult decisions with significant ramifications. It is a mathematical reality that error cannot be completely avoided and, in fact, efforts to reduce the likelihood of one type of error will automatically result in an increase in the opposite type of error. Agencies must decide the acceptable level of risk and liability and provide appropriate training to their personnel in line with that risk.


Corrective action plans emphasizing retraining and remediation versus discipline and punishment are more appropriate in response to officers who make mistakes, have misjudgments, or err in making these split-second decisions. Law enforcement personnel at every level need to increase their sophistication and understanding of the scientific research that defines the limits of human performance; focus on improving the training of all personnel, including investigators; and use this opportunity to enhance public dialog with the intent of minimizing conflict resulting from unrealistic expectations of officer performance. Public trust can be maintained through thorough education and investigations with serious discipline for those rare officers who betray the public trust by willfully manipulating the details of a critical incident.


Lessons Learned


• There are no “superhuman” people. Physical and mental limitations are the same for everyone. No exceptions.


• An understanding of the factors that contribute to errors in perception, performance, and inaccurate incident recall is essential for the modern-day law enforcement officer, investigator, supervisor, manager, and executive.


• Agencies must analyze their own use-of-force patterns and develop training scenarios that mimic lighting, distraction, movement (predominantly lateral) by both the officer and the suspect, and task complexity (pursuit followed by a shooting, hand-to-hand struggle followed by a shooting), including comparable physical and emotional exhaustion levels.


• Training must occur on a repetitive basis so that the officers develop a high level of proficiency and confidence in their performance. The exact frequency of training will vary based on a combination of individual characteristics, prior experience, and job demands.


• The scenario training should be videotaped and include the officer recounting verbally and in writing the incident details in a manner similar to what would occur following an actual incident. This will provide the officer first-hand experience of the factors affecting perception, performance, and memory recall and provide the necessary feedback loop to further refine performance.


• Scientific and practical limitations governing human performance must be taken into account when evaluating performance.


• Corrective action plans in response to mistakes and misjudgments made as a result of split-second decisions should emphasize retraining and remediation.




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Dr. Audrey Honig is head of Psychological Services for the Los Angeles Sheriff’s Department, a position she has held for 22 years. She is chair of the Police Psychological Services Section of the International Association of the Chiefs of Police. She is a noted presenter on interviewing and interrogation techniques.


Dr. William Lewinski is a professor in the Law Enforcement Program at Minnesota State University, Mankato. He is also the founder and director of the Force Science Research Center at MSUM. He has over 30 years of experience studying officer involved deadly force encounters.