Hotspot detection aims to find sub-regions of a space that have higher probability density of generating certain events (e.g., disease, crimes) than the other regions. Finding hotspots has important applications in many domains including public health, crime analysis, transportation, etc. Existing methods of hotspot detection rely on test statistics (e.g., likelihood ratio, density) that do not consider spatial nondeterminism, leading to false and missing detections. We provide theoretical insights into the limitations of related work, and propose a new framework, namely, Nondeterministic Normalization based scan statistic (NN-scan), to address the issues. We also propose a DynamIc Linear Approximation (DILA) algorithm to improve NN-scan’s efficiency. In experiments, we show that NN-scan can significantly improve the precision and recall of hotspot detection and DILA can greatly reduce the computational cost.