Modelling established and emerging crime hotspots in a period of rapid homicide growth using spatio-temporal Hawkes processes

Understanding where and how violent crime concentrates and evolves is central to effective place-based policing. We examine homicides in Guayaquil, Ecuador, between 2014 and 2024 using a semi-parametric spatio-temporal Hawkes process to identify, characterise and track the hotspot locations. The framework allows direct evaluation of three propositions from the criminology of place (spatial concentration, temporal stability of hotspots, and short-term crime contagion) by decomposing crime risk into a background component capturing baseline risk and a self-exciting component capturing triggering dynamics, and by tracking their evolution over time using annual measures of spatial concentration and hotspot exceedance sets. The results demonstrate that spatial concentration persists but reorganises under rapid homicide growth. Fewer than 7% of grid cells account for 50% of homicides across the period, yet the share of cells required to account for 75% of triggered events rises from close to 1% before 2020 to around 7.5% in 2022 and 2023. Self-exciting dynamics dominate in the south of the city, while the north exhibits persistently elevated background risk. These findings support place-based crime prevention during periods of rapid growth and underline the importance of distinguishing structurally persistent hotspots from those driven by short-term contagion when prioritising locations for intervention.