Objectives This randomised controlled trial tested the effect of immediate versus delayed, as well as repeated, questioning on memory retrieval regarding details of officer-involved shootings.

Methods A sample of 87 police officers experienced “active armed offender” training scenarios followed by a memory questionnaire testing their recall and recognition of details of the scenario. Officers were randomly assigned to one of two experimental groups. Group 1 completed the questionnaire immediately after the training scenario and again 2 days later, while group 2 completed the survey 2 days later only.

Results Linear mixed models showed that delayed questioning negatively impacted officers’ recognition of correct details of the incident, but only for details not directly associated with threat stimuli. This pattern was supported by the free recall data. Further, officers who were questioned immediately did not experience the same memory decay over time, showing that early questioning can aid memory retention. Officers were also better at recognising correct threat-relevant details (compared to non-threat relevant) that were visual, but the reverse was true for auditory details.

Conclusions We found no support for the position that delay improves officers’ memory. However, rather than finding universal memory decay over time, the interaction between timing and type of details being recalled revealed a more nuanced picture. This knowledge assists understanding of the limitations of information provided by officers under different interviewing conditions.