Excited delirium syndrome (ExDS): Situational factors and risks to officer safety in non-fatal use of force encounters

Abstract Study objective Police use of force (UoF) encounters include individuals with Excited Delirium Syndrome (ExDS) with some frequency. Situational factors and risks to officer safety associated with these encounters have not been well studied. We examined the likelihood that subjects displaying various concomitant features of ExDS were under the influence of drugs and/or alcohol. We also examined the extent of subject violence, and the impact of this behaviour on the encounter (e.g., the odds of a struggle). Greater understanding of the prevalence of ExDS and the specific risk it represents to law enforcement officers and the subjects they encounter will guide appropriate policy and response strategies. Methods A prospective evaluation of a consecutive cohort of subjects involved in UoF encounters with police was conducted. Data were collected from January 2012 to December 2015. Consistent with previous research, the presence of six or more features was used to identify probable cases of ExDS. The odds that subjects in a state of probable ExDS were under the influence of drugs and/or alcohol was calculated and compared against subjects who exhibited less than three features of ExDS. In addition, the violent nature of subjects (e.g., the odds of a subject being in possession of a weapon) displaying various concomitant features of the syndrome was examined. The number of sudden and unexpected arrest-related death (ARDs) was documented. Results UoF occurred in 9006 of 10.9 million police-public interactions (0.08%). Of the UoF encounters, 156 (1.7%) subjects displayed six or more features of ExDS. With four recorded sudden and unexpected ARDs of violent and agitated subjects in our cohort, up to 6.3% of these subjects experiencing probable ExDS could be expected to be at risk of sudden death. Logistic regression analyses indicated that there were significantly higher odds that subjects exhibiting more features of ExDS (e.g., six or more) were under the influence of drugs. On the other hand, there were significantly lower odds that individuals exhibiting ExDS were under the influence of alcohol alone. In addition, those displaying a greater number of features demonstrated higher odds of engaging in assaultive behaviour, presenting a threat of grievous bodily harm or death, and being involved in a struggle that went to the ground with an officer. A slight increase in the presence of weapons was observed in encounters with probable ExDS. Conclusion Our study provides important information to guide the development of policy and procedure in law enforcement. Police encounter a subject with ExDS 1 in every 58 UoF incidents (1.7%). Those individuals are at higher odds of being intoxicated with drugs according to officers' assessments and at risk of being further exerted during a struggle on the ground, both of which appear to play a major role in deaths associated to ExDS. There is a demonstrable increase in risk to officers and public safety from the violent behaviour displayed by subjects presenting a greater number of features of ExDS. Our data suggests that up to 6.3% of subjects in a state of ExDS could succumb to ARDs; however, we cannot comment on the prevalence of death for persons with ExDS who do not encounter police. Further research is needed to determine which force options optimize outcome for police and subjects. Additionally, research surrounding pathophysiology leading to death should focus on subjects with six or more features of ExDS. Ultimately, a better understanding in this area will contribute to improving the outcomes of these encounters for those suffering from ExDS and those tasked with assisting them.