<p>The use of deadly force by police has garnered significant public and academic attention, yet the absence of comprehensive national data remains a substantial obstacle to accountability, transparency, and research. The current study evaluates key unofficial databases that document deadly police force, examining their inclusion criteria, strengths, and limitations. While unofficial sources are more comprehensive than official datasets, particularly those that include non-fatal events, they each vary in their inclusion criteria. These discrepancies hinder efforts to accurately assess the prevalence and correlates of deadly police force, particularly at the national level. This report outlines best practices for researchers, underscoring the importance of aligning data selection with research objectives and acknowledging data limitations.</p>