Another study also deserves attention. Researchers surveyed 265 police officers from the Midwest who were exposed to three stressful conditions: a live-fire simulation, a video of the training that included the shooting, and a video of the simulation scene without sound or a shooting. Most of the officers were not questioned about their experiences until 12 weeks later, but a sample of the officers participated in a “rehearsal” interview—they answered the questions immediately after the exposure and then again 12 weeks later.

The researchers concluded that, overall, stress was positively related to memories of armed people, unrelated to memories of unarmed people, and negatively related to objects.⁸ Their findings echoed other research that suggested eyewitnesses focus on the source of the threat or stress (e.g., the shooter) more intensely than the peripheral information about a scene or incident (e.g., the furniture in the room where the shooting occurred).⁹ Interestingly, the study also found that the officers subjected to the immediate rehearsal questioning recalled clearer memories in their second interview 12 weeks later compared with the officers interviewed only once.

This study is important for several reasons. First, it showed that during high-stress events, officers more likely will focus on a threat, rather than peripheral objects or people. If an officer vividly remembers a person with a weapon but has only a blurred vision of an unarmed individual or an object in the room or area, this does not necessarily indicate that the officer’s testimony is a conscious deception, planned response, or otherwise illegitimate. Instead, these distortions may be caused by stress—the research indicated that officers’ memories after a traumatic event can play tricks on them or vary from reality. This might result from pressure or anxiety caused by the incident, officers’ exhaustion during the event, or other factors that influence memory.¹⁰

Second, the study supported the argument that it remains unclear as to when officers should be interviewed concerning their observations, actions, and reactions after an OIS. Many ambiguities exist regarding this issue, and, thus, no proven best practices exist for collecting information from officers involved in an OIS. However, most agencies follow the intuition that exhausted, injured, or otherwise impaired officers should not be questioned immediately after a traumatic event. Otherwise, not only does this pose serious risks to the officers’ health and well-being but information gleaned from these interviews may sabotage an investigation. These case studies indicated that through no fault of their own, these officers’ memories may suffer from distortions due to the stress caused by such traumatic incidents. As such, investigators must keep these factors in mind when determining the timing and structure of post-OIS interviews.

Authors’ Study

To look at this phenomenon more closely, the authors organized a pilot study in December 2010 to examine how officers recall high-stress events. They used the Richland County, South Carolina, Sheriff’s Department as the subject of their study. The researchers surveyed officers’ reactions to training that involved live-fire simulation and role play by interviewing the officers and analyzing their responses.¹¹

The department periodically conducts training activities that involve these live-fire simulations. This instance involved a group of deputies learning to respond to active-shooter situations in schools. The training occurred in an abandoned school that realistically emulated a real world environment. Officers responded to one of two active-shooter scenarios: a school shooting or a terrorist attack. Each simulation involved similar reportable and measurable characteristics.

During the simulation, officers worked in teams to clear a building, assist victims or hostages, and secure suspects. Following the incident, each deputy attended a short debriefing. When the training concluded for the day, half of the officers (Group A) wrote a report detailing the event. Then, the researchers asked Group A to recount the event again 3 days later. The other half of the officers (Group B) were required only to detail their recollections of the event after 3 days passed but were not asked to write a report immediately after the training.

By dividing the subjects into these two groups, the study aimed to determine whether officers’ memories were sharper and more accurate in the time immediately following the shooting or sometime later. Also, Group A’s rehearsal interview would help illustrate how their memories of a high-stress event changed over time.

Officers’ memories were evaluated based on their ability to recall five elements of the event and the level of specificity that they provided. These five items were divided into two categories: threat variables and environmental variables. Each correct assessment of one of these elements earned officers a certain amount of points.

Each report was assessed based on how accurately the officers could remember the five threat and environmental variables, and the deputies’ scores in each category were summed to arrive at an overall score. Then, the total scores of all officers within the two groups were averaged.

Findings

When officers in Group A detailed the event immediately after the simulation, their total score averaged 7.5 with a high score of 12 and a low score of 4 (out of 14 points possible). Three days later, when Group A’s officers provided their recollections for the second time, their average score improved to 7.8 with a high score of 13 and a low score of 4. The total score for Group B’s officers, who only provided their recollections 3 days after the simulation, averaged 6.4 with a high score of 10 and a low score of 2.

These results demonstrated that the deputies’ memories remained sharper when asked to recount the incident immediately after it occurred, compared with the deputies who were not asked until a few days had passed. Additionally, the memories of individuals asked to share their recollections immediately after the incident improved slightly in their second report.

The researchers analyzed these results further by distinguishing officers’ scores for threats versus environmental variables. A separate analysis of these scores (with a maximum score of 7 for each category) showed that the deputies recalled threats more accurately than environmental variables. Group A received an average score of 4.4 for threat variables compared with 3.3 for environmental variables. Also, the results revealed that officers’ recollections of threats weakened slightly over time as their score for threat variables decreased to 4.2. The subjects did not remember environmental variables as accurately in either condition. Group A showed an average score of 3.3 immediately after the event and 3.5 after 3 days passed. Group B averaged 3.3.

Although the differences were not drastic, they demonstrated that, overall, the deputies maintained stronger memories of threats (e.g., the people and weapons that could harm them), rather than the environment (i.e., the conditions under which the event occurred). Additionally, asking officers to recall facts immediately after an event may prove important for collecting accurate threat-related information because the officers’ memories of threats weakened slightly after time passed.¹² This could suggest that for investigators to obtain the most precise information about an OIS, it might be best for them to ask officers about threat-related information as soon as possible. Conversely, it may not be as urgent to interview witnesses about environmental variables right away.

Because this study involved a simulation, the subjects were not at risk for the same type of exhaustion, injury, or other impairments that can affect officers’ memories after a real live-fire incident. But, the major lesson from this pilot study remains that these deputies recalled the threat variables better than environmental factors, and they remembered them best immediately after the incident.

Policy Implications

Although a pilot study with significant limitations, this research presents important information for policy makers who determine whether an OIS investigation should involve immediate or delayed interviews of officers. Currently, no law enforcement-wide best practice or proven method exists for the timing of these interviews. However, several influential sources have suggested guidelines.

The Police Assessment Resource Center conducted a study of the Portland, Oregon, Bureau of Police and subsequently recommended that the department’s internal affairs investigators interview officers who were involved in or witnessed an OIS no later than a few hours after the event.¹³ Conversely, the International Association of Chiefs of Police stated in Police Psychological Services guidelines that investigators should give officers time to recover after the incident before they conduct any detailed interviewing, with this recovery time ranging from a few hours to overnight. Other experts echoed this recommendation; they suggested that officers may make more accurate and thorough statements if they are allowed to wait at least 24 hours before questioning, giving the officers time to rest and recuperate before they make a formal declaration.¹⁴

Many agencies embraced these suggestions and implemented policies requiring officers to wait before giving an interview or speaking to an investigator about an OIS. In this respect, these departments treat officers differently than they do suspects or civilian witnesses. If agencies think that officers involved in a traumatic event provide better accounts after a waiting period, then why are witnesses and suspects interviewed as soon as possible after the incident? Prior research consistently determined that individuals’ memories react strangely to stressful or traumatic events—officers and civilians alike experience perceptual and memory distortions after these incidents. What remains unknown, however, is what factors influence the distortions and how to minimize them.

To this end, it might be best for agency protocol to allow for case-by-case flexibility when determining the timing and structure of interviews following an OIS. Investigators must remain sensitive to personnel who have just experienced one of the most traumatic events in the life of a police officer but also strive to obtain the most accurate information possible about the incident. For example, if investigators need precise intelligence about the incident, then it may be important for them to give the officers and civilian witnesses an initial walk-through of the incident without providing details. This walk-through may function as the “rehearsal” interview that helps trigger better memory recall later on as demonstrated in the authors’ study. Similarly, an expert highlighted the value of this time delay in the interview process, stating that interviewers can consider “…providing enough brief information during an immediate on-scene ‘walk-through’ to get the investigation started.”¹⁵

Also, investigators should remain sensitive to the fact that individual officers can react to an OIS differently. Some personnel handle the stress of a shooting better than others, and depending on the outcome of the event, it may be necessary to delay some detailed interviews. For example, if the officers’ or witnesses’ friends or family suffered injuries, investigators may need to delay asking them to rehash the incident in great detail. Additionally, if individuals are exhausted, injured, or otherwise impaired, they will not provide meaningful information for any type of fact-finding mission. The decision of when to conduct post-OIS interviews should balance the humanistic concerns for the witnesses with the investigators’ need for information.

Even officers employed by the same department and who received the same training may react differently to an OIS; as such, they could display varying levels of detail and accuracy in their recollections of the event. Officers’ ages, backgrounds, and life experiences can impact significantly how they will respond to an OIS. Far too often, officers who suffer postshooting trauma feel further pressure from department administrators anxious for information. This practice could be counterproductive because anything that causes the witness additional stress may hamper memory or recall. Putting pressure on officers by forcing them to recount a traumatic event too soon may result in incomplete and inaccurate information, possibly leading to grave errors in an investigation.

Conclusion

Clearly, more rigorous and precise research must focus on the factors that influence memory distortions and how to minimize them. Researchers have not reached a consensus on how to trigger more accurate memories of stressful events. Additionally, most investigators fail to anticipate the natural distortions, which likely occur due to expected variance rather than deception, that likely will appear in officers’ memories. Until a greater understanding of these issues is reached, inconsistencies and inaccuracies in eyewitness testimonies will continue to hamper OIS investigations. Department leaders and personnel alike must acknowledge the many unpredictable factors that influence the memories of the involved officers after an OIS to ensure a successful investigation.